Tone Curve Research Articles

Tone Curve Stabilization for Color Electrophotography

Color accuracy and consistency is crucial for printing. In order to compensate for fluctuations in consumables and environmental factors associated with electrophotography (EP), calibrations are performed at specific intervals to maintain color quality. During a calibration, color patches are printed on either paper or the transfermedia and EP process parameters are adjusted based on the density measurements of the patches. Since each calibration may require additional time and consumables, it is desirable to increase the interval of calibration as well as to reduce the number of calibration patches. In this paper, an algorithm to improve color consistency while reducing consumable consumption and increasing calibration interval is proposed. The algorithm utilizes statistical model prediction. The proposed algorithm can adapt the EP process to compensate for consumable usage and measurable environmental factors with minimal number of calibration patches. The effectiveness of the proposed algorithm is validated using an off-the-shelf in-line color EP printer under different environmental conditions as well as different consumable usage models.

Controling color of liquid‐crystal displays

Abstract— Two newly derived characterization models for a liquid‐crystal (LC) display have been tested for five LC‐based displays. Data measured from a series of test colors indicated that all LC‐based displays showed similar characteristics, including an S‐shaped tone curve and poor channel chromaticity constancy. Because they include a hyperbolic function in their definition, the models do not have analytical inverses, and so iterative mathematical techniques are applied. It was shown that a new characterization model based on a hyperbolic function fits the tone curve very accurately with only four coefficients per channel for any type of LCD. In addition, it was also shown that the first derivative of the function provides a means of accurate correction of the chromaticity variation.

Digital photogrammetry for air-photo-based construction of a digital elevation model over snow-covered areas ‐ Blamannsisen, Norway

Digital elevation models (DEMs) have been constructed over snow-covered and glaciated areas from 11 air photos optimized during production using a semi-automatic contrast-adjusting method called dodging. Construction of the DEMs from the air photos was accomplished using IMAGINE OrthoMAX software. In general, the results of the DEM construction are promising. Analytical and visual comparisons of GPS field data and published maps with the constructed DEMs indicate a high degree of agreement, with an average difference better than 2.8 m for most of the area. Errors and spurious data cells appear to have been minimized throughout most of the DEMs. One height anomaly, an erroneous peak with a height of between c. 250 m and 1200 m above the actual elevation, persistently appeared in one of the DEMs, despite numerous attempts to address the issue. Enhancements during the air-photo scanning process, such as sharpening and applying a tone curve, have been found to have a beneficial effect in reducing such erroneous results.

Method and device for speech recognition

A method and device for recognizing dialectal variations in a language. From an incoming speech is on one hand a speech recognition procedure being performed, and on the other hand the fundamental tone curve being extracted. Out of the speech recognition is created an allophone string which together with the fundamental tone curve is used for the detecting of the maximun and minimum values of the fundamental tone. The recognized speech is compared with a lexicon with orthography and transcription for the finding of suitable word candidates. The found word candidates are further analyzed regarding syntax. This in mentioned way found syntactical and lexical information is used for creating a model of the speech. The fundamental tone outline of the model and the fundamental tone of the speech are compared, at which the maximun and minimum values of the fundamental tones are appointed and a difference between the model and the speech are obtained. The difference is after that influencing the model which is brought to correspond to the given speech. The in mentioned way modelled model is then used for the speech recognition, at which an increased possibility to understand the different dialects of a language in an artificial way is achieved.

Acoustical evaluation of the municipal theatre of Lima, Perú

An exploratory evaluation carried out at the Municipal Theatre of Lima, Perú, in order to establish the acoustical quality of the auditorium, is described. Through a graphical analysis on the various floors in the theatre, for several theoretical sources on the stage, the covering and homogeneous distribution of the sound and the early time delay gap for the main floor and the two balconies is determined. The diverse acoustical measurements carried out in the unoccupied hall in just one day, allow for a layout of the real tone curve of the theatre for the six fundamental frequencies, as well as the background noise levels. The results are presented through ray diagram plans and reverberation time and noise criteria curves.

Control of tone reproduction characteristics by time constant of development roller in monocomponent development

The authors describe the relationship between the resistance of a development roller and the development characteristics of a monocomponent development system. To investigate this relationship the authors developed an electric field neutralization model by considering a virtual electrode determined by the time constant of a resistive layer on a development roller. From a simulation model and experimental results, the authors find that the tone reproduction curve for development gamma is strongly dependent on the layer time constant. When the time constant is smaller than the development time, gamma is determined by neutralization of the development electric field. When the time constant is larger than the development time, gamma is determined by a counter charge left on the development roller after toner is deposited on the photoreceptor. It became possible to vary the tone curve over a wide range by the time constant of development roller in monocomponent development.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The automatic tone decay test as part of dynamic measurement of threshold.

Only dynamic recording of the tone threshold can give information on pathologic adaptation, auditory fatigue, and aggravation. We have therefore automated the tone decay test. This was achieved by modifying the Grason-Stadler audiometer E 800 and, concurrently, by developing a special device with integrated circuits for this purpose. The print-out is made by a commerical x-y-recorder which is also used for recording the impedance test results. During the automatic tone decay test the patient himself increases the intensity of the tone only until he can hear the tone again, the intensity of the tone otherwise remaining constant. Thus, we obtain either a flat (adaptation) or a sharply declining (auditory fatigue) curve which correlates with the Békésy continuous tone curve, but may show a distinctive separation. The tone decay test is - in contrast to all other suprathreshold tests - independent of the amount of hearing loss. It can therefore give information on the kind of hearing impairment for normal short duration thresholds as well.