Indranil Sinharoy

Active computational imaging for circumventing resolution limits at macroscopic scales

Macroscopic imagers are subject to constraints imposed by the wave nature of light and the geometry of image formation. The former limits the resolving power while the latter results in a loss of absolute size and shape information. The suite of methods outlined in this work enables macroscopic imagers the unique ability to capture unresolved spatial detail while recovering topographic information. The common thread connecting these methods is the notion of imaging under patterned illumination. The notion is advanced further to develop computational imagers with resolving power that is decoupled from the constraints imposed by the collection optics and the image sensor. These imagers additionally feature support for multiscale reconstruction.

Structured Light Optical Super-Resolution: Encoding for Limited Optical Bandwidth

Structured illumination finds widespread use in microscopy and optical profilometry. A marriage of the principle underlying these methods promises novel solutions to the resolution problem that plagues consumer cameras.

Pushing the limits of digital imaging using structured illumination

The present work describes an active stereo apparatus that can not only recover scene geometry but also resolve spatial detail beyond the camera optical cutoff. The apparatus is comprised of a camera and a projector whose center-of-perspective is located in the camera pupil plane1. The scene is illuminated with warped sinusoidal patterns as opposed to periodic or coded patterns. The findings reported in this work can help design imaging systems that feature improved optical resolution and 3D acquisition capabilities.

Geometric model for an independently tilted lens and sensor with application for omnifocus imaging

Optical imaging systems in which the lens and sensor are free to rotate about independent pivots offer greater degrees of freedom for controlling and optimizing the process of image gathering. However, to benefit from the expanded possibilities, we need an imaging model that directly incorporates the essential parameters. In this work, we propose a model of imaging which can accurately predict the geometric properties of the image in such systems. Furthermore, we introduce a new method for synthesizing an omnifocus (all-in-focus) image from a sequence of images captured while rotating a lens. The crux of our approach lies in insights gained from the new model.

Space-Variant Optical Super-Resolution using Sinusoidal Illumination

The present work extends the scope of Optical Super-Resolution to imaging systems with spatially-varying blur, by using sinusoidal illumination. It also establishes that knowledge of the space-variant blur is not a pre-requisite for super-resolution.

Geometric model of image formation in Scheimpflug cameras

We present a geometric model of image formation in Scheimpflug cameras that is most general. Scheimpflug imaging is commonly used is scientific and medical imaging either to increase the depth of field of the imager or to focus on tilted object surfaces. Existing Scheimpflug imaging models do not take into account the effect of pupil magnification (i.e. the ratio of the exit pupil diameter to the entrance pupil diameter), which we have found to affect the type of distortions experienced by the image-field upon lens rotations. In this work, we have also derived the relationship between the object, lens and sensor planes in Scheimpflug configuration, which is very similar in form with the standard Gaussian imaging equation, but applicable for imaging systems in which the lens plane and the sensor plane are arbitrarily oriented with respect to each other. Since the conventional rigid camera, in which the sensor and lens planes are constrained to be parallel to each other, is a special case of the Scheimpflug camera, our model also applies to imaging with conventional cameras.

Omnifocus image synthesis using lens swivel

We present a simple technique for synthesizing an infinite depth of field image from a sequence of photographs captured while rotating a symmetric lens about the center of the entrance pupil. We discuss the feasibility conditions and provide a Zemax simulation that verifies the method.

Optical super resolution using a lattice of light spots

The paper outlines a super resolution strategy that overcomes the severe anisotropy in the resolving power of a single-lens imager, by processing images acquired under a lattice of light spots.

A critical review of the slanted-edge method for color SFR measurement

Critical examination of the slanted-edge method for color SFR measurement reveals inaccuracies in the estimated SFR, due to the use of demosaicing. The proposed method resolves these inaccuracies by eliminating the need for demosaicing during SFR measurement.