Imaging systems have numerous applications in industrial, military, consumer, and medical settings. Assembling a complete imaging system requires the integration of optics, sensing, image processing, and display rendering. This issue features original research ranging from design of stimuli for human perception, optics applications, and image enhancement to novel imaging modalities in both color and infrared spectral imaging, gigapixel imaging as well as a systems perspective to imaging.
© 2014 Optical Society of America
Imaging systems have numerous applications in industrial, military, consumer, and medical settings. Assembling a complete imaging system requires the integration of optics, sensing, image processing, and display rendering. This feature issue is aimed at scientists, engineers, and practitioners interested in understanding how different materials, and components combine with image processing to determine and influence image system performance. The design of optical systems must factor the system as an integrated unit and optimize the performance for a given application. There are numerous disciplines that are needed for the design and advancement of an optical system. These disciplines include imaging optics; optical detection; computational, adaptive, and compressive imaging; displays; and usability of information—they all contribute to defining the system. Scientists and engineers from commercial, academic, and military disciplines came together to share advances in imaging systems at the OSA Imaging Systems and Applications (IS) Topical Meeting in 2013 (Arlington, Virginia). This issue contains a subset of the high-quality work presented at this meeting, as well as some contributions from the wider imaging systems’ community. These papers cover a broad spectrum of theoretical and experimental investigations in imaging systems and applications.
In this collection of papers, you will find research on computationally efficient video restoration for Nyquist-sampled imaging sensors; spectral imaging by combining transverse-field-detector and color-filter arrays; continuum fusion solutions for replacement target models in electro-optic detection; image enhancement of objects with highly dynamic brightness and large rotational motion; a video-rate nine-band multispectral SWIR sensor; design of pictorial stimuli for perceptual experiments; characterization of a 2-Gpixel-wide field-of-view visible imager; a compact camera for multispectral and conventional imaging based on patterned filters; and analytical direct solutions of the Risley prism systems for tracking and pointing.
Ricci et al. show methods for video restoration that are computationally efficient and simultaneously based on physics-informed assumptions about image formation, including Poisson noise and the diffraction limit. For Nyquist-sampled imagery, the authors combine pixelwise temporal Kalman filtering for noise reduction with adaptive Wiener filtering for resolution enhancement. Their method can account for global-scene motion as well as local motion. The computational complexity is sufficiently low that the proposed method can run in real time with possible applications in airborne imaging and surveillance.
Martinez et al. propose an improved spectral imaging sensor by combining a transverse-field detector with a color filter array. The authors designed and performed experiments to test the influence of different design features on the estimation quality and also compared its performance with other traditional spectral imaging systems. Their results show that systems combining a transverse-field detector with a color filter array performed better than systems with the same type of multispectral-color filter array on other detectors, or even the same transverse-field detectors combined with different kinds of filters used in common imaging systems.
Schaum discusses the general problem of detecting target signals that are not additive, but instead replace some part of a background signal. This is a relevant signal model in imaging, for example, in the case of detecting an opaque subpixel target in a hyperspectral image. It is then necessary to test the hypothesis of the target being present, but without knowing the fraction of the target in the pixel. Schaum employs his original “continuum-fusion” concept to tackle this problem and derives families of new detectors that can be expressed in closed form.
Kanaev et al. report on the application of multiframe superresolution to sampling limited imagery that models space objects. They analyze the motion-estimation errors from the standpoint of an optical-flow-interpolation-error metric and show dependence of the object-tracking estimation on brightness changes and on the pixel displacement values between subsequent images. Spatial-acuity enhancement was obtained with a resolution enhancement.
Farnand and Fairchild studied the optimal design of pictorial stimuli for effective and efficient perceptual experiments with the goal of understanding the impact of image content on visual attention and consistency of experimental results. They apply this understanding to develop guidelines for pictorial-target design for perceptual-image-comparison experiments. It is shown that, along with scene complexity, the image modifications and the difficulty of the image-equivalency decisions played a role in the experimental response.
Marks et al. present a 2-Gpixel camera built around a single objective lens of monocentric design, i.e., with only concentric spherical surfaces. An array of up to 382 subcameras is placed around the objective lens, each covering a part of the full field of view. MTF measurements show good performance, and the paper also presents simple observer tests. The image presentation concept is radically different from conventional cameras in that only the part of the image requested by the user is actually rendered. Apart from their primary use in surveillance, these cameras are likely to be used for detailed recordings of large scenes of interest such as sports events and landscapes.
Skauli et al. describe a design for a compact camera that allows for multispectral and conventional imaging based on utilization of striped patterned filters in the focal plane combined with scanning of the field of view. This approach allows for both multispectral and conventional 2D imaging in a single, compact, low-cost architecture. The potential volume-size reduction is of the order of several hundred for comparable traditional imaging systems.
Kutteruf et al. take the use of patterned filters a step further and present a nine-band multispectral camera capable of video-rate-snapshot imaging. The camera employs a filter array with repeating cells of different pixel-sized bandpass filters attached directly to an InGaAs image sensor operating in the 1–1.7 μm spectral range. The paper discusses the spectral response, pixel alignment, and radiometric calibration of the camera. The recorded images are in good agreement with hyperspectral images of the same scene. This technology has a clear potential for use in military systems as well as many emerging applications using the short wave infrared spectral range.
Peng et al. use the Risley prism systems, composed of two wedge prisms, for tracking and pointing applications. The authors derive the analytical direct solutions of the Risley prism systems from the expressions of the direction cosines of the wedge prism through the coordinate transformation. The exact expressions obtained for the problem of high performance tracking are generalized to investigate the synthesis of tracking of a given target by controlling the circular motion of the two prisms.