From the Publisher: 
The accessible presentation of this book gives both a general view of the entire computer vision enterprise and also offers sufficient detail to be able to build useful applications. Users learn techniques that have proven to be useful by first-hand experience and a wide range of mathematical methods. A CD-ROM with every copy of the text contains source code for programming practice, color images, and illustrative movies. Comprehensive and up-to-date, this book includes essential topics that either reflect practical significance or are of theoretical importance. Topics are discussed in substantial and increasing depth. Application surveys describe numerous important application areas such as image based rendering and digital libraries. Many important algorithms broken down and illustrated in pseudo code. Appropriate for use by engineers as a comprehensive reference to the computer vision enterprise.

Computer vision : a modern approach = 计算机视觉 : 一种现代的方法

Near infrared spectroscopy: A mature analytical technique with new perspectives - A review.

Spectrometers with ever-smaller footprints are sought after for a wide range of applications in which minimized size and weight are paramount, including emerging in situ characterization techniques. We report on an ultracompact microspectrometer design based on a single compositionally engineered nanowire. This platform is independent of the complex optical components or cavities that tend to constrain further miniaturization of current systems. We show that incident spectra can be computationally reconstructed from the different spectral response functions and measured photocurrents along the length of the nanowire. Our devices are capable of accurate, visible-range monochromatic and broadband light reconstruction, as well as spectral imaging from centimeter-scale focal planes down to lensless, single-cell-scale in situ mapping.

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Single-nanowire spectrometers

Thanks to some technical progress in interferencefilter design based on different technologies, we can finally successfully implement the concept of multispectral filter array-based sensors. This article provides the relevant state-of-the-art for multispectral imaging systems and presents the characteristics of the elements of our multispectral sensor as a case study. The spectral characteristics are based on two different spatial arrangements that distribute eight different bandpass filters in the visible and near-infrared area of the spectrum. We demonstrate that the system is viable and evaluate its performance through sensor spectral simulation.

Multispectral Filter Arrays: Recent Advances and Practical Implementation

The adoption of spectral imaging by industry has so far been limited due to the lack of high speed, low cost and compact
spectral cameras. Moreover most state-of-the-art spectral cameras utilize some form of spatial or spectral scanning
during acquisition, making them ill-suited for analyzing dynamic scenes containing movement. This paper introduces a
novel snapshot multispectral imager concept based on optical filters monolithically integrated on top of a standard
CMOS image sensor. It overcomes the problems mentioned for scanning applications by snapshot acquisition, where an
entire multispectral data cube is sensed at one discrete point in time. This is enabled by depositing interference filters per
pixel directly on a CMOS image sensor, extending the traditional Bayer color imaging concept to multi- or hyperspectral
imaging without a need for dedicated fore-optics. The monolithic deposition leads to a high degree of design flexibility.
This enables systems ranging from application-specific, high spatial resolution cameras with 1 to 4 spectral filters, to
hyperspectral snapshot cameras at medium spatial resolutions and filters laid out in cells of 4x4 to 6x6 or more. Through
the use of monolithically integrated optical filters it further retains the qualities of compactness, low cost and high
acquisition speed, differentiating it from other snapshot spectral cameras.

A compact snapshot multispectral imager with a monolithically integrated per-pixel filter mosaic

Although the potential of hyperspectral imaging has been demonstrated for several applications, using laboratory setups
in research environments, its adoption by industry has so far been limited due to the lack of high speed, low cost and
compact hyperspectral cameras. To bridge the gap between research and industry, we present a novel hyperspectral
sensor that integrates a wedge filter on top of a standard CMOS sensor. To enable the low-cost processing of a
microscopic wedge filter, we have introduced a design that is able to compensate for process variability. The result is a
compact and fast hyperspectral camera made with low-cost CMOS process technology. The current prototype camera
acquires 100 spectral bands over a spectral range from 560 nm to 1000 nm, with a spectral resolution better than 10 nm
and a spatial resolution of 2048 pixels per line. The speed is 180 frames per second at illumination levels as typically
used in machine vision. The prototype is a hyperspectral line scanner that acquires 16 lines per spectral band in parallel
on a 4 MPixel sensor. The theoretic line rate for this implementation is thus 2880 lines per second.

A compact, high-speed, and low-cost hyperspectral imager

Although the potential of spectral imaging has been demonstrated in research environments, its adoption by industry has so far been limited due to the lack of high speed, low cost and compact spectral cameras. We have previously presented work to overcome this limitation by monolithically integrating optical interference filters on top of standard CMOS image sensors for high resolution pushbroom hyperspectral cameras. These cameras require a scanning of the scene and therefore introduce operator complexity due to the need for synchronization and alignment of the scanning to the camera. This typically leads to problems with motion blur, reduced SNR in high speed applications and detection latency and overall restricts the types of applications that can use this system. This paper introduces a novel snapshot multispectral imager concept based on optical filters monolithically integrated on top of a standard CMOS image sensor. By using monolithic integration for the dedicated, high quality spectral filters at its core, it enables the use of mass-produced fore-optics, reducing the total system cost. It overcomes the problems mentioned for scanning applications by snapshot acquisition, where an entire multispectral data cube is sensed at one discrete point in time. This is achieved by applying a novel, tiled filter layout and an optical sub-system which simultaneously duplicates the scene onto each filter tile. Through the use of monolithically integrated optical filters it retains the qualities of compactness, low cost and high acquisition speed, differentiating it from other snapshot spectral cameras based on heterogeneously integrated custom optics. Moreover, thanks to a simple cube assembly process, it enables real-time, low-latency operation. Our prototype camera can acquire multispectral image cubes of 256x256 pixels over 32 bands in the spectral range of 600-1000nm at a speed of about 30 cubes per second at daylight conditions up to 340 cubes per second at higher illumination levels as typically used in machine vision applications.

A snapshot multispectral imager with integrated tiled filters and optical duplication

Spectral imaging can reveal a lot of hidden details about the world around us, but is currently confined to laboratory environments due to the need for complex, costly and bulky cameras. Imec has developed a unique spectral sensor concept in which the spectral unit is monolithically integrated on top of a standard CMOS image sensor at wafer level, hence enabling the design of compact, low cost and high acquisition speed spectral cameras with a high design flexibility. This flexibility has previously been demonstrated by imec in the form of three spectral camera architectures: firstly a high spatial and spectral resolution scanning camera, secondly a multichannel snapshot multispectral camera and thirdly a per-pixel mosaic snapshot spectral camera. These snapshot spectral cameras sense an entire multispectral data cube at one discrete point in time, extending the domain of spectral imaging towards dynamic, video-rate applications. This paper describes the integration of our per-pixel mosaic snapshot spectral sensors inside a tiny, portable and extremely user-friendly camera. Our prototype demonstrator cameras can acquire multispectral image cubes, either of 272x512 pixels over 16 bands in the VIS (470-620nm) or of 217x409 pixels over 25 bands in the VNIR (600-900nm) at 170 cubes per second for normal machine vision illumination levels. The cameras themselves are extremely compact based on Ximea xiQ cameras, measuring only 26x26x30mm, and can be operated from a laptop-based USB3 connection, making them easily deployable in very diverse environments.

A tiny VIS-NIR snapshot multispectral camera

Colony counting is a procedure used in microbiology laboratories for food quality monitoring, environmental
management, etc. Its purpose is to detect the level of contamination due to the presence and growth of bacteria, yeasts
and molds in a given product. Current automated counters require a tedious training and setup procedure per product and
bacteria type and do not cope well with diversity. This contrasts with the setting at microbiology laboratories, where a
wide variety of food and bacteria types have to be screened on a daily basis. To overcome the limitations of current
systems, we propose the use of hyperspectral imaging technology and examine the spectral variations induced by factors
such as illumination, bacteria type, food source and age and type of the agar. To this end, we perform experiments
making use of two alternative hyperspectral processing pipelines and compare our classification results to those yielded
by color imagery. Our results show that colony counting may be automated through the automatic recovery of the
illuminant power spectrum and reflectance. This is consistent with the notion that the recovery of the illuminant should
minimize the variations in the spectra due to reflections, shadows and other photometric artifacts. We also illustrate how,
with the reflectance at hand, the colonies can be counted making use of classical segmentation and classification
algorithms.

Nicolaas Tack

Papers

A compact snapshot multispectral imager with a monolithically integrated per-pixel filter mosaic

A compact, high-speed, and low-cost hyperspectral imager

A snapshot multispectral imager with integrated tiled filters and optical duplication

A tiny VIS-NIR snapshot multispectral camera

Towards a colony counting system using hyperspectral imaging