No study to-date explored the relationship between perceived image quality (IQ) and perceived depth (DP) in
stereoscopic medical images. However, this is crucial to design objective quality metrics suitable for stereoscopic
medical images. This study examined this relationship using volume-rendered stereoscopic medical images for both
dual- and single-view distortions. The reference image was modified to simulate common alterations occurring during
the image acquisition stage or at the display side: added white Gaussian noise, Gaussian filtering, changes in luminance,
brightness and contrast. We followed a double stimulus five-point quality scale methodology to conduct subjective tests
with eight non-expert human observers. The results suggested that DP was very robust to luminance, contrast and
brightness alterations and insensitive to noise distortions until standard deviation σ=20 and crosstalk rates of 7%. In
contrast, IQ seemed sensitive to all distortions. Finally, for both DP and IQ, the Friedman test indicated that the quality
scores for dual-view distortions were significantly worse than scores for single-view distortions for multiple blur levels
and crosstalk impairments. No differences were found for most levels of brightness, contrast and noise distortions. So,
DP and IQ didn’t react equivalently to identical impairments, and both depended whether dual- or single-view distortions
were applied.
In this paper we investigate the performance of a transparent photoconductive sensor based on a double layer of organic materials (m-MTDAB / PTCBI) which are deposited on two interdigitated transparent ITO electrodes. The performance of the sensor is demonstrated with electro-optical measurements: the I(V) curves consist of two linear sections meeting at a knee voltage Vt. Linear regression performed on the I(V) curves below Vt show that the conductance is a power law of the luminance incident on the device. We present a model to describe the behaviour of the sensor below Vt. We present measurements of I(t) for a transient illumination of the sensor. Plotting the inverse of the current as a function of time we find that the transient is consistent with the model for voltages below Vt. For voltages above Vt we find that the sensor behaves like a resistor in series with a space charge (SC) region. We present a local illumination experiment that confirms the existence of a SC region between the electrodes of the photoconductive sensor for V<Vt. The space charge region is located near the cathode of the sensor.
MTF (Modular Transfer Function) is used as a metric for the sharpness of the images displayed on a monitor. However,
MTF is often only measured in one dimension (usually horizontally or vertically). The goal of this work is to provide a
methodology that allows measuring the MTF of a display correctly in 2D. Existing methodologies are analyzed to
determine if they are satisfactory. We concluded that all of the currently used methodologies have shortcomings. To
overcome the limitations of the existing technologies, a new methodology is introduced, the Pixel Spread Function. In
this methodology, an impulse to the display is approximated by a single lit pixel, on a uniform background. The
measurements are performed at a very close distance, to limit the degradations introduced by the measurement system.
By applying signal processing, the 2D MTF has been obtained for this methodology. After averaging the results for
multiple images and pixel positions and removing the camera degradation, the methodology proved to be reproducible
and easy to perform. To validate the proposed methodology, a mathematical model has been created that allows
simulating the MTF. Since the geometrical structure of the pixel has the largest impact on the obtained result, the model
is based on it. Other degradations in the system (aberrations, diffraction...) are approximated by an additional blurring
step. The theoretical and experimental results were compared, and it was concluded that the methodology is valid.
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