This paper presents a new type of electroplated nickel micromachined probe with out-of-plane predeformation for next generation integrated circuit (IC) chip testing probe card applications. The probe card was fabricated using silicon bulk micromachining, titanium (Ti) deposition, nickel (Ni) electroplating and laser scribing processes. We use the effect of the residual stresses of thin-film deposition on flexible micromachined probes to produce a large out-of-plane predeformation and combine the post-electroplating technique to further increase the probe's thickness and therefore enhance its stiffness. The typical micromachined probe had a thickness of 10–25 µm, a width of 20 µm and a length of 150 µm. The maximum out-of-plane deflection of the fabricated nickel probe was approximately 55 µm. The probe's pitch can be designed to be less than 50 µm to meet the demands of fine pad pitch probing. This probe card is potentially capable of providing a very large number of micromachined probes in an array format, and this is designed also to satisfy the requirements for high resolution and low cost wafer-level testing.
E-reading devices are becoming more and more common in our daily life, and they are used under a wide range of ambient light levels, from completely dark to extremely bright conditions. In this study, a psychophysical experiment is carried out to investigate how ambient light level affects the visual comfort of an e-reading device. Human observers compare the visual comfort of pairs of different text-background lightness combinations on a tablet device under three ambient light levels (i.e., 150, 1500, and 15,000 lx). With our previous work, the experimental results show that the trend of visual comfort interval scales below 1500 lx (i.e., Dark, 150, 300, and 1500 lx) are similar to each other but not for those under illuminance above the 1500 lx (i.e., 3000 and 15,000 lx). For the same lightness difference between text and background, the observers tend to read the text with a white background compared to a black background, especially for 3000 and 15,000 lx. Moreover, a black text on a light-gray background is the most comfortable combination under these two illuminance levels. An evaluation model is proposed based on ambient illuminance, screen parameters, and visual estimation to design an optimal viewing condition when reading on the tablet display.
Three psycho-visual experiments were carried out to investigate visual afterimage characteristics of high luminance LEDs under dark surround conditions. The results show that the luminance of illumination, exposure time and background luminance are the primary factors influencing the afterimage’s duration, the color difference between stimulus and background, and visibility. Besides, visual afterimage characteristics are strongly correlated with the luminance contrast between the stimulus and the background, but not for the color difference with a white background. A third-order polynomial regression model was proposed to accurately estimate the afterimage duration, the color difference between stimulus and background, and visibility. The model performance showed high R-squared, low root-mean-square error (RMSE) and mean absolute error (MAE) values between the predicted and visual characteristics.
In the study, two psychophysical experiments are carried out to understand the visual comfort and white appearance of a tablet display. Twenty-four observers assess the visual comfort of document layouts, and eleven observers rate the whiteness percentage of the stimulus under normal
light levels with a CCT of 6500 K. The result of the experiment for visual comfort indicates that a combination of black text with a light grey background presents the better visual comfort. On the other hand, the finding of the white appearance experiment shows that the observers rate the
stimulus with CCT of 6515 K and a Duv of 0 as the whitest.
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