The yellow-ring (YR) is a chromatism phenomenon which is caused by the inhomogeneous phosphor layer of the whitelight
LED (WLED) and can be observed from the projected WLED lightspot. In general, the lights emitted from a
WLED will focus on the specific range to form a circular lightspot; in the meanwhile, the YR will appear on the
periphery of this lightspot. In our previous study, the evaluation of YR phenomenon was graded by the YR index (YRI),
which is the product of the yellow light intensity (Y) and total light intensity (I). Therein, the maximum value of YRI is
a crucial optical parameter for determining the YR degree and a YR evaluation model is as the criterion for quality
control of WLED. In this article, the YR distribution of MR-16 triplet lens module related to the distance (pitch) between
two of three WLEDs will be discussed. Experimental results show that the YRI of triple lens WLED module is lower
than one of single lens WLED module due to the overlapped effect of WLED lightspots. In addition, the YR degree of
triplet lens WLED module will be lower if the pitch is longer, but the unintended dark-corner effect will appear when the
pitch is enough longer.
In this paper, 2 sub machine vision based alignment systems were used to establish a high speed alignment system for screen printing. It can be used on the solar cell and flat display panel manufacture. The 2 sub alignment system can auto align target simultaneously. When one target was takes out, another target can implement auto alignment simultaneously. It can save the wait time for target take out procedure. The sub alignment system includes 4 CCD cameras, 4 lens, 4 outer coaxial LED light sources, a vacuum table and a 3 axis motorized stage. The alignment accuracy is about 1 μm.
The skin illuminated of two lights at different wavelength can be applied to detect the oxygen saturation of human blood. Due to the absorption coefficient of oxy- (HbO<sub>2</sub>) and deoxy- (Hb) hemoglobin are different at the wavelength 660 nm and 890 nm, the transmitted and reflected light within the skin can be used to compute the oxygen saturation image of skin. However, the intensities of skin images illuminated by a 20 mW NIR-LED are too low to determine the position of blood vessel when acquired by the color CCD camera. In order to improve the disadvantages, a mono camera was used and the irradiated distance and angle between LED light and test hand were adjusted to acquire the higher resolution and contrast blood vessel images for the oxygen saturation calculation. In the experiment, we developed the suitable angle to irradiate NIR light is at 75 degrees because the reflected and scattered effect could be generated significantly from both vertical and horizontal direction. In addition, the best contrast vessel images can be obtained when the shutter time is set at 44.030 ms and the irradiated distance was at the range 140-160 mm due to the intensity ratio between tissue and vessel region is the highest and the intensities of image would not be saturated or become too low when these two parameters were adjusted slightly. In future, the proposed parameters and results can be applied to the oxygen saturation measurement in the clinical diagnosis.
Fluorescence objects can be excited by ultraviolet (UV) light and emit a specific light of longer wavelength in
biomedical experiments. However, UV light causes a deviation in the blue violet color of fluorescent images. Therefore,
this study presents a color deviation adjustment method to recover the color of fluorescent image to the hue observed
under normal white light, while retaining the UV light-excited fluorescent area in the reconstructed image. Based on the
Gray World Method, we proposed a non-linear logarithm method (NLLM) to restore the color deviation of fluorescent
images by using a yellow filter attached to the front of a digital camera lens in the experiment. Subsequently, the
luminance datum of objects can be divided into the red, green, and blue (R/G/B) components which can determine the
appropriate intensity of chromatic colors. In general, the datum of fluorescent images transformed into the CIE 1931
color space can be used to evaluate the quality of reconstructed images by the distribution of x-y coordinates. From the
experiment, the proposed method NLLM can recover more than 90% color deviation and the reconstructed images can
approach to the real color of fluorescent object illuminated by white light.