Recently, we presented a new OCR-concept  for historic prints. The core part is the glyph recognition based on pattern matching with patterns that are derived from computer font glyphs and are generated on-the-fly. The classification of a sample is organized as a search process for the most similar glyph pattern. In this paper, we investigate several similarity measures which are of vital importance for this concept.
Perceived color is an empirical phenomenon and, to date, is only approximately understood in complex situations.
In general, color spaces or color order systems, as a mathematical characterization of such empirical observations,
address specific applications such that they may not be adequate in other contexts. In this work, we investigate
four device-independent color spaces (color order systems) with regard to their suitability for a specific gamut
mapping concept called "unsharp mapping".
Contrary to high dynamic range imaging, the preservation of details and the avoidance of artifacts is not explicitly considered
in popular color management systems. An effective way to overcome these difficulties is image filtering. In this
paper we investigate several image filter concepts for detail preservation as part of a practical gamut mapping strategy.
In particular we define four concepts including various image filters and check their performance with a psycho-visual
test. Additionally, we compare our performance evaluation to two image quality measures with emphasis on local
contrast. Surprisingly, the most simple filter concept performs highly efficient and achieves an image quality which is
comparable to the more established but slower methods.
Even though gamut mapping (GM) is a three-dimensional polyhedron problem, algorithmically it is usually not
treated as such. This is due to tight runtime constraints in practice, which suggest simple algorithms. We will
show that basic geometric operations, like the intersection of a ray with the gamut surface, can be implemented
very efficiently for typical GM applications that work with device gamuts. This opens up new possibilities to
design algorithms without reducing their practicability.
This work presents a model for dotgain prediction using repetitive patterns based on the characterization of
neighboring and clustering effects of a specific printing device. Estimating dotgain is done nowadays by measuring
patches of color patterns realized by a specific printing device. Current models use the information about adjacent
dots to predict dotgain. However, research has shown that dotgain is influenced by the neighborhood of a dot
which in general is bigger than one dot-size, in particular in connection with laser printers. The presented method
predicts the dotgain of a dot considering a larger surrounding based on the observation of two main parameters
affecting the luminance of a pattern which can be fitted using linear regression.
In principal, color reproduction on specific devices can be divided into transformation of color coordinates and the
adaptation of colors to a device, called gamut mapping. The well established ICC color management neglects the
latter aspect. This paper presents a practical implementation addressing both an eficient color transformation
and a sophisticated gamut mapping.
We treat image-to-device gamut mapping as a multi-criteria optimization problem. Our approach leads to a parameterized mathematical optimization problem that allows to constrain the degree to which objectives like contrast preservation, hue preservation, saturation preservation and the continuity of the mapping can be violated while maximizing the device gamut exploitation. We demonstrate the feasibility of our approach on several benchmark image- and device gamuts.
The design of a gamut mapping algorithm (GMA) is always a compromise between preserving different competing aspects such as color, contrast, and lightness. A natural requirement of a GMA is that the algorithmic treatment of this competition has to avoid any additional artifacts such as discontinuities or loss of contrast. In this work, several common gamut mapping algorithms are studied from this aspect, resulting in the observation that problems with geometric discontinuities are widespread. For the assessment of the phenomena induced by local mapping properties, an algorithmic test is developed and applied. This new test supports both the quality check of existing as well as the development of new GMAs.
The design of a gamut mapping algorithm (GMA) is always a compromise between preserving different competing aspects such as color, contrast and lightness. A natural requirement to a GMA is that the algorithmic treatment of this competition has to avoid any additional artefacts such as discontinuities or loss of contrast. In this paper several common gamut mapping algorithms are studied from this aspect, resulting in the observation that problems with geometric discontinuities are widespread. For the assessment of the phenomena induced by local mapping properties, an algorithmic test was developed and applied. This new test supports both, the quality check of existing as well as the development of new GMAs. Finally we present a first new algorithm designed to have a good behavior concerning continuity and contrast conservation which also performs well in classical psychophysical tests.
We present a new method for the computation of both, image and device gamut boundaries. The method has been designed to bypass the quality vs. time trade off that one usually faces when computing gamut boundaries. This trade off is between the geometric accuracy of the boundary and the time it takes to compute it. Our method is geometrically accurate in the sense that the computed gamut boundary tightly encloses the color points that make up the gamut. At the same time it is fast compared to other methods. Thus it can be used in an image-dependent gamut mapping approach. The underlying concept of the presented method is a data structure that we call discrete flow complex which is derived from the discrete distance function to the color points. We have implemented the method and tested it with a suite of test images. Our experimental results show that the method is in fact fast and geometrically accurate. In the future we plan to use the gamut boundaries computed by our method for fast, high-quality, image-dependent gamut mapping in three dimensions.
We report on an IC lithographic resolution study in which APEX-E resist on polysilicon coated wafers was exposed to synchrotron x radiation through a high-resolution mask that contained Au-electroplated features ranging in size from 0.5 down to 0.15-micrometers . Exposures were made at mask-to-substrate gaps ranging from 20 to 35 micrometers and at doses from 100 to 134 mJ/cm2. We probed the wafers with an SEM, both before and after etch, and electrically. From the electrical linewidth probing, we found that for isolated lines and 1:2 L:S patterns the feature widths were linear down to 0.18-micrometers . For the 1:1 and 2:1 L:S arrays, the widths were linear down to 0.25-micrometers . Dense and isolated lines down to 0.25-micrometers exhibited +/- 15% dose latitude over a 10-micrometers gap range. Contact holes were examined only by SEM. The smallest size that printed was nominally 0.225 micrometers , but was measured to be 0.20-micrometers after etch. Critical dimension uniformity, calculated with each feature type allowed its own mean value, was approximately equals 40 nm (3(sigma) ), including intrafield and across wafer variation. The mask CD uniformity was approximately equals 30 nm (mean + 3(sigma) ). The wafer-to-wafer CD variation was found to be 6 nm (3(sigma) ) and the electrical test-to-test CD variation was 3 nm (3(sigma) ). We use regression analysis to separate the component of CD variation that is assignable to intrafield form that assignable to interfield. The regression analysis to separate the component of CD variation that is assignable to intrafield from that assignable to interfield. The regression analysis indicates that these components of CD variation are systematic rather than random. The main contributor to the interfield component may be polysilicon etch. The intrafield error is believed to be caused predominantly by beamline nonuniformity and not by errors on the 1x mask.
To further improve the performance of alignment systems for high resolution lithographic exposure systems, the various contributions to the overall alignment accuracy must be identified and separately reduced. We have measured the contributions to the performance of the ALX100 alignment system of the SUSS XRS200 x-ray stepper emerging from recognition repeatability, focus setting, and gap setting. We have found asymmetric alignment profiles during the alignment of a metal-layer process wafer combined with stepfield dependent offsets. After modification of the signal evaluation the stepfield dependent offset was largely reduced and the performance increased.
Overlay accuracy is known as one of the most important subjects for ULSI device production. Significant contributions such as alignment accuracy and mask distortions are well known. By breaking the 100 nm range on overlay accuracy a number of influences have to take into account, which were usually neglected for relaxed design rules. One of these influences to the overlay is directly related to wafer distortions induced by flatness deviations of wafer chucks. This impact was characterized by investigating the elastic behavior of 4' wafers (525 micrometers thick), fixed on a wafer chuck. Induced elastical deformation due to flatness error of the chuck causes strains and elongations in the wafer surface and therefore wafer distortions. The results obtained by exposure experiments and calculations show that even a point size defect has a 30 mm spreading. Therefore the induced distortions arrives about 100 nm in case of a 3 micrometers flatness irregularity. The final result of the investigations induces that the flatness differences between different wafer chucks or steppers should be smaller than 1 micrometers for design rules below quarter micron.
Demands on advanced exposure tools for ULSI applications have increased rapidly during the last few years. Overlay accuracy, one of the key subjects, has been under continuous development. In X-ray lithography the overlay is mainly determined by pattern displacement on X-ray masks, by process-induced wafer distortions and by stepper-related contributions, generated by a limited alignment accuracy and displacements during the pattern replication. It is the aim of this paper to characterize the stepper-related contributions to the overlay budget. For this purpose we investigated the overlay performance of vertical XRS-200 type X-ray steppers equipped with an advanced optical alignment system. Using a multiple exposure technique, a series of alignment experiments were performed on typical CMOS layers. The results show that the wafer chuck flatness has, beside the alignment accuracy, a major influence on the overlay accuracy.