Edge detection can be of great importance to image processing in various digital imaging applications such as digital
television and camera. Therefore, extracting more accurate edge properties are significantly demanded for achieving a
better image understanding. In vector gradient edge detection, absolute difference of RGB values between a center pixel
value, and its neighborhood values are usually used, although such a device-dependent color space does not account for
human visual characteristics well. The goal of this study is to test a variety of color difference equations and propose the
most effective model that can be used for the purpose of color edge detection. Three of synthetic images generated using
perceptibility threshold of the human visual system were used for objectively evaluate to 5 color difference equations
studied in this paper. A set of 6 complex color images was also used to testing the 5 color difference equations
psychophysically. The equations include ΔRGB, ΔE*ab, ΔECMC, CIEDE2000 (ΔE00) and CIECAM02-UCS delta E
(ΔECAM-UCS). Consequently, there were not significant performance variations observed between those 5 color difference
equations for the purpose of edge detection. However, ΔE00 and ΔECAM-UCS showed slightly higher mean opinion score
(MOS) in detected edge information.
The purpose of this study can be divided into two descriptions. First, we investigated perceived brightness contrast to
varied surround luminance levels from dark to over-bright conditions by measuring psychophysical data using magnitude
estimation. As a result, the perceived brightness contrast increases until surround changes from dark to average, it
decreases from average to over-bright. Second, so obtained experimental results are compared with brightness contrast
estimates of CIECAM028 and MobileCAM9 and we refined a surround factor c and brightness correlate Q of CIECAM02. Consequently, the refined results appear matched to brightness contrast. A Pearson correlation between the
refined CIECAM02 prediction and the visual results was 0.95.
Much research has shown that perceived image contrast increases as the surround luminance increases, but a number of recent studies reported opposite trends under higher surround luminance levels. We measured the change in perceived image contrast under a wide range of surround luminance levels covering from dark up to 2087 cd/m2. A large-area illuminator was used to illuminate the surround. It consists of 23 dimmable fluorescent lamps and a diffuser. Its maximum luminance is 2087 cd/m2 and could be adjusted to six lower levels. A set of paired comparison experiments was conducted to compare the perception of image contrast under seven different surround luminance levels. The results showed that the perceived image contrast varies with surround luminance and the maximum perceived image contrast is found near a surround ratio (SR) of 1. As SR increases from 0 to 1, the z score is increased, which can be fully expected by the Bartleson and Breneman effect. However, it is drastically decreased in the region of SR > 1; thus, the perceived image contrast is eventually decreased.
The relationship between input DAC count and output luminance in CRT display varies according to the “brightness” control. In this study the effect of brightness adjustment on the accuracy of color reproduction in CRT display is shown experimentally. The optimum brightness level of test monitor has been measured by using a device developed in our laboratory. The accuracy of the simplified color reproduction model is evaluated for three monitor setups, which is controlled to optimum, low, and high brightness level. To prove the experimental results, the channel additivity and chromaticity constancy assumptions are tested for three setups. With the color difference ?E*u'v' between predicted and measured values for 215 colors, it can be ascertained that the brightness must be adjusted to optimum level to enhance the accuracy.
Object color is defined by the surface spectral reflectance. However, the output signal of an image sensor device is affected by the other physical factors. The output signal for the same object color is different according to the device characteristics. The spectral sensitivity of an image sensor device is the most important factor. To recover the original color from the output signal, two kinds of studies are performed. One is to develope a spectral sensitivity measurement system and the other is to obtain color characteristic vectors which can represent a wide variety of any spectral reflectance accurately.
Strains under three dimensional deformation are determined from holographic interferometric fringe. For a cantilever beam subjected to the combined forces of out-of plane and in-plane deflection, holographic interferometric fringes are obtained experimentally. From a fringe pattern, the effect of the out-of plane deflection and the in-plane deflection are analysed, respectively. The 3rd order polynomial of displacement distribution is obtained using regression method. Therefore strain can be determined from the second derivative of the polynomial. The experimental result is compared with the numerical analysis by finite element method.
The simple and effective optical arrangement synthesizing holographic fringe and speckle photography is presented. This optical system is based on image holography. Cantilever beam located on the precision translator is used to evaluate this system. Experimental results agree well with the actual displacements within the error of 5%. The measurement of 3-D contact deformation is demonstrated as an its application.
The optical technique combined the holographic interferometry and speckle photography was applied to measure three dimensional deformation. Out-of-plane and in-plane displacements of the contact deformation were determined experimentally and compared with the numerical analysis. The experimental results are in good agreement with the numerical results.