Efficient use of bit planes in the generation of motion stimuli

The production of animated motion sequences on computer-controlled display systems presents a technical problem because large images cannot be transferred from disk storage to image memory at conventional frame rates. A technique is described in which a single base image can be used to generate a broad class of motion stimuli without the need for such memory transfers. This technique was applied to the generation of drifting sine-wave gratings (and by extension, sine wave plaids). For each drifting grating, sine and cosine spatial phase components are first reduced to 1 bit/pixel using a digital halftoning technique. The resulting pairs of 1-bit images are then loaded into pairs of bit planes of the display memory. To animate the patterns, the display hardware's color lookup table is modified on a frame-by-frame basis; for each frame the lookup table is set to display a weighted sum of the spatial sine and cosine phase components. Because the contrasts and temporal frequencies of the various components are mutually independent in each frame, the sine and cosine components can be counterphase modulated in temporal quadrature, yielding a single drifting grating. Using additional bit planes, multiple drifting gratings can be combined to form sine-wave plaid patterns. A large number of resultant plaid motions can be produced from a single image file because the temporal frequencies of all the components can be varied independently. For a graphics device having 8 bits/pixel, up to four drifting gratings may be combined, each having independently variable contrast and speed

Digital Color Imaging

This paper surveys current technology and research in the area of digital color imaging. In order to establish the background and lay down terminology, fundamental concepts of color perception and measurement are first presented us-ing vector-space notation and terminology. Present-day color recording and reproduction systems are reviewed along with the common mathematical models used for representing these devices. Algorithms for processing color images for display and communication are surveyed, and a forecast of research trends is attempted. An extensive bibliography is provided

Prediction of screener-induced moire in digital halftone pattern generation

In the graphic arts, objectionable moire patterns are often observed on films or printed products due to the interaction of various periodic structures of halftone images. A particular type of moire pattern that results from digital halftoning at arbitrary angles and frequencies using a virtual screen function has been studied. A computer program was developed that produces uniform digital halftone patterns using a virtual screen approach and that calculates the corresponding amplitude spectra. It was found that aliasing due to the sampling of the virtual screen causes low frequency components in the amplitude spectrum. Moire patterns with fundamental vector frequencies equal to those of the strong aliased components were observed in halftone images reconstructed on a film recorder. Moire was also observed at frequencies not represented or under represented in the amplitude spectrum. It is shown that this moire effect is due to the additive beating of two or more higher frequency components that differ by the frequency of the observed moire. It is suggested that the non-linearities of the film recording process amplify this effect . The effects on the resulting moire patterns of varying the halftone parameters of dot size, dot shape, screen angle, and screen frequency were examined. In general, the amplitude spectra are complex, indicating many overlapping patterns. Screener induced moire was found to behave in a nearly identical manner to that induced by digital scanning of an existing halftone

Robustness of a DFT based image watermarking method against am halftoning

U ovom radu je evaluirana otpornost na rastriranje metode označavanja slika bazirane na diskretnoj Fourierovoj transformaciji (DFT). Rastriranje se koristi za reprodukciju višetonskih slika. U istraživanju je korišten set od 1000 slika. Za rastriranje su korištena tri različita oblika rasterskog elementa (točka, elipsa i linija) i 5 različitih linijatura (10, 13, 15, 40 i 60 lin/cm). Evaluirana je vjerojatnost detekcije i distribucija postignutih vrijednosti detekcije. Rezultati su pokazali da je ispitivana metoda označavanja slika otporna na rastriranje linijaturama većim od 15 lin/cm. Također, zaključeno je da oblik rasterskog elementa ima slab utjecaj na stupanj detekcije.In this paper the robustness of a Discrete Fourier Transform (DFT) based image watermarking scheme to amplitude modulation (AM) halftoning is evaluated. Halftoning is used for reproduction of continuous images. Thus, it is important that a watermarking method is robust to halftoning. Three different shapes of clustered dots of AM (Amplitude Modulation) halftones are used (round, ellipse and line) with five different halftone frequencies (10, 13, 15, 40, and 60 line/cm). The tests where done on a dataset of 1000 images. As the metric of robustness, watermark detection rate, distribution of detection values, and ROC (Receiver Operation Characteristic) curves were used. The results showed that the watermarking scheme is robust to halftoning for halftone frequencies greater than 15 line/cm. Also, the type of AM halftone used has almost no effect on a detection rate

Robustness of a DFT based image watermarking method against am halftoning

U ovom radu je evaluirana otpornost na rastriranje metode označavanja slika bazirane na diskretnoj Fourierovoj transformaciji (DFT). Rastriranje se koristi za reprodukciju višetonskih slika. U istraživanju je korišten set od 1000 slika. Za rastriranje su korištena tri različita oblika rasterskog elementa (točka, elipsa i linija) i 5 različitih linijatura (10, 13, 15, 40 i 60 lin/cm). Evaluirana je vjerojatnost detekcije i distribucija postignutih vrijednosti detekcije. Rezultati su pokazali da je ispitivana metoda označavanja slika otporna na rastriranje linijaturama većim od 15 lin/cm. Također, zaključeno je da oblik rasterskog elementa ima slab utjecaj na stupanj detekcije.In this paper the robustness of a Discrete Fourier Transform (DFT) based image watermarking scheme to amplitude modulation (AM) halftoning is evaluated. Halftoning is used for reproduction of continuous images. Thus, it is important that a watermarking method is robust to halftoning. Three different shapes of clustered dots of AM (Amplitude Modulation) halftones are used (round, ellipse and line) with five different halftone frequencies (10, 13, 15, 40, and 60 line/cm). The tests where done on a dataset of 1000 images. As the metric of robustness, watermark detection rate, distribution of detection values, and ROC (Receiver Operation Characteristic) curves were used. The results showed that the watermarking scheme is robust to halftoning for halftone frequencies greater than 15 line/cm. Also, the type of AM halftone used has almost no effect on a detection rate

Direct imaging of a digital-micromirror device for configurable microscopic optical potentials

Programable spatial light modulators (SLMs) have significantly advanced the configurable optical trapping of particles. Typically, these devices are utilized in the Fourier plane of an optical system, but direct imaging of an amplitude pattern can potentially result in increased simplicity and computational speed. Here we demonstrate high-resolution direct imaging of a digital micromirror device (DMD) at high numerical apertures (NA), which we apply to the optical trapping of a Bose-Einstein condensate (BEC). We utilise a (1200 x 1920) pixel DMD and commercially available 0.45 NA microscope objectives, finding that atoms confined in a hybrid optical/magnetic or all-optical potential can be patterned using repulsive blue-detuned (532 nm) light with 630(10) nm full-width at half-maximum (FWHM) resolution, within 5% of the diffraction limit. The result is near arbitrary control of the density the BEC without the need for expensive custom optics. We also introduce the technique of time-averaged DMD potentials, demonstrating the ability to produce multiple grayscale levels with minimal heating of the atomic cloud, by utilising the high switching speed (20 kHz maximum) of the DMD. These techniques will enable the realization and control of diverse optical potentials for superfluid dynamics and atomtronics applications with quantum gases. The performance of this system in a direct imaging configuration has wider application for optical trapping at non-trivial NAs.Comment: 9 page

The development of the toner density sensor for closed-loop feedback laser printer calibration

A new infrared (IR) sensor was developed for application in closed-loop feedback printer calibration as it relates to monochrome (black toner only) laser printers. The toner density IR sensor (TDS) was introduced in the early 1980’s; however, due to cost and limitation of technologies at the time, implementation was not accomplished until within the past decade. Existing IR sensor designs do not discuss/address: • EMI (electromagnetic interference) effects on the sensor due to EP (electrophotography) components • Design considerations for environmental conditions • Sensor response time as it affects printer process speed The toner density sensor (TDS) implemented in the Lexmark E series printer reduces these problems and eliminates the use of the current traditional “open-loop” (meaning feedback are parameters not directly affecting print darkness such as page count, toner level, etc.) calibration process where print darkness is adjusted using previously calculated and stored EP process parameters. The historical process does not have the ability to capture cartridge component variation and environmental changes which affect print darkness variation. The TDS captures real time data which is used to calculate EP process parameters for the adjustment of print darkness; as a result, greatly reducing variations uncontrolled by historical printer calibration. Specifically, the first and primary purpose of this research is to reduce print darkness variation using the TDS. The second goal is to mitigate the TDS EMI implementation issue for reliable data accuracy

Digital halftoning using fibonacci-like sequence pertubation and using vision-models in different color spaces

A disadvantage in error diffusion is that it creates objectionable texture patterns at certain gray levels. An approach, threshold perturbation by Fibonacci-like sequences, was studied. This process is simpler than applying a vision model and it also decreases the visible patterns in error diffusion. Vector error diffusion guarantees minimum color distance in binarization provided that a uniform color space is used. Four color spaces were studied in this research. It was found that vector error diffusion in two linear color spaces made no reduction in the quality of halftoning compared with that in CIEL*a*b* or CIEL*u*v* color spaces. A luminance vision MTF and a chroma vision MTF were used in model-based error diffusion to further improve the halftone image quality

Signal processing based solutions for holographic displays that use binary spatial light modulators

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Science of Bilkent University, 2012.Thesis (Ph. D.) -- Bilkent University, 2012.Includes bibliographical references leaves 141-156.Holography is a promising method to realize satisfactory quality threedimensional (3D) video displays. Spatial light modulators (SLM) are used in holographic video displays. Usually SLMs with higher dynamic ranges are preferred. But currently existing multilevel SLMs have important drawbacks. Some of the associated problems can be avoided by using binary SLMs, if their low dynamic range is compensated for by using appropriate signal processing techniques. In the first solution, the complex-valued gray level SLM patterns that synthesize light fields specified in the non-far-field range are halftoned into binary SLM patterns by solving two decoupled real-valued constrained halftoning problems. As the synthesis region, a sufficiently small sub-region of the central diffraction order region of the SLM is chosen such that the halftoning error is acceptable. The light fields are synthesized merely after free space propagation from the SLM plane and no other complicated optical setups are needed. In this respect, the theory of halftoning for ordinary real-valued gray scale images is extended to complex-valued holograms. Simulation results indicate that light fields that are given either on a plane or within a volume can be successfully synthesized by our approach. In the second solution, a new full complex-valued combined SLM is effectively created by forming a properly weighted superposition of a number of binary SLMs where the superposition weights can be complex-valued. The method is a generalization of the well known concepts of bit plane decomposition and representation for ordinary images and actually involves a trade-off between dynamic range and pixel count. The coverage of the complex plane by the complex values that can be generated is much more satisfactory than that is achieved by those methods available in the literature. The design is also easy to customize for any operation wavelength. As a result, we show that binary SLMs, with their robust nature, can be used for holographic video display designsUlusoy, ErdemPh.D