Abstract: In today’s world, the LED display has been used for
presenting visual information under various circumstances. Such
information is an important intermediary in the human information
processing. Researchers have been investigated diverse factors that
influence this process effectiveness. The letter size is undoubtedly
one major factor that has been tested and recommended by many
standards and guidelines. However, viewing information on the
display from direct perpendicular position is a typical assumption
whereas many actual events are required viewing from the angles.
This current research aims to study the effect of oblique viewing
angle and viewing distance on ability to recognize alphabet, number,
and English word. The total of ten participants was volunteered to our
3 x 4 x 4 within subject study. Independent variables include three
distance levels (2, 6, and 12 m), four oblique angles (0, 45, 60, 75
degree), and four target types (alphabet, number, short word, and
long word). Following the method of constant stimuli our study
suggests that the larger oblique angle, ranging from 0 to 75 degree
from the line of sight, results in significant higher legibility threshold
or larger font size required (p-value < 0.05). Viewing distance factor
also shows to have significant effect on the threshold (p-value
Abstract: Speckle phenomena results from when coherent
radiation is reflected from a rough surface. Characterizing the speckle
strongly depends on the measurement condition and experimental
setup. In this paper we report the experimental results produced with
different parameters in the setup. We investigated the factors which
affects the speckle contrast, such as, F-number, gamma value and
exposure time of the camera, rather than geometric factors like the
distance between the projector lens to the screen, the viewing distance,
etc. The measurement results show that the speckle contrast decreases
by decreasing F-number, by increasing gamma value, and slightly
affects by exposure time of the camera and the gain value of the
camera.