The traditional frame accumulation technology can effectively reduce the random noise and improve the signal-to-noise ratio in the image. A frame accumulation technology with superimposed sawtooth-shaped-function can reduce the quantization noise and increase the grayscale resolution. However, in the case of continuous operating environment, it is not suitable because constant amplitude light used must be turned off for taking pure and shadowy images, which are generated by superimposed shaped light. To solve this problem, we propose an improved method named dual optical signals with different periods (DOSDP) to improve grayscale resolution of an image. The method does not need to capture signals twice. In other situations, where it is not appropriate to directly superimpose a shaped function optical signal to an object, a piece of glass is installed on the light path between the camera and the object so that the superimposed light can enter the camera through the glass reflection. Furthermore, our method allows superimposed signals to be nonlinear. Experimental results show that DOSDP method can effectively improve quality of the image.
A medical endoscope system combined with the narrow-band imaging (NBI), has been shown to be a superior diagnostic tool for early cancer detection. The NBI can reveal the morphologic changes of microvessels in the superficial cancer. In order to improve the conspicuousness of microvessel texture, we propose an enhanced NBI method to improve the conspicuousness of endoscopic images. To obtain the more conspicuous narrow-band images, we use the edge operator to extract the edge information of the narrow-band blue and green images, and give a weight to the extracted edges. Then, the weighted edges are fused with the narrow-band blue and green images. Finally, the displayed endoscopic images are reconstructed with the enhanced narrow-band images. In addition, we evaluate the performance of enhanced narrow-band images with different edge operators. Experimental results indicate that the Sobel and Canny operators achieve the best performance of all. Compared with traditional NBI method of Olympus company, our proposed method has more conspicuous texture of microvessel.
Quantization operation in the imaging process rounds the measured values of intensities into integers. It neglects the possible differences between the intensities having the same rounded numbers, and therefore lowers the grayscale resolution of images. Although some methods have been proposed for the reconstruction of high-grayscale resolution images from multiple subpixel-shifted low-spatial-resolution and low-grayscale-resolution images, the problems of nonsmooth transition within regions and insufficient intensity levels still exist. A grayscale superresolution method based on fill light and a photographing apparatus are proposed to deal with the problems. The photographing apparatus can add fill lights with slightly different intensities to the captured images without changing the brightness of scenes. Our reconstruction method is based on the method of estimating a float number from several rounded integers. Then, a high-grayscale-resolution image is reconstructed from multiple low-grayscale-resolution images with slightly different intensity fill lights. Simulated data and real-world data have been used for the evaluation of the method, and the experimental results show that our method effectively improves the grayscale resolution. Besides, our method is convenient for a graphics processing unit implementation.
We propose an innovative and efficient approach to improve K-view-template (K-view-T) and K-view-datagram (K-view-D) algorithms for image texture classification. The proposed approach, called the weighted K-view-voting algorithm (K-view-V), uses a novel voting method for texture classification and an accelerating method based on the efficient summed square image (SSI) scheme as well as fast Fourier transform (FFT) to enable overall faster processing. Decision making, which assigns a pixel to a texture class, occurs by using our weighted voting method among the "promising" members in the neighborhood of a classified pixel. In other words, this neighborhood consists of all the views, and each view has a classified pixel in its territory. Experimental results on benchmark images, which are randomly taken from Brodatz Gallery and natural and medical images, show that this new classification algorithm gives higher classification accuracy than existing K-view algorithms. In particular, it improves the accurate classification of pixels near the texture boundary. In addition, the proposed acceleration method improves the processing speed of K-view-V as it requires much less computation time than other K-view algorithms. Compared with the results of earlier developed K-view algorithms and the gray level co-occurrence matrix (GLCM), the proposed algorithm is more robust, faster, and more accurate.
Spectral clustering method has been widely used in image segmentation. A key issue in spectral clustering is how to
build the affinity matrix. When it is applied to color image segmentation, most of the existing methods either use
Euclidean metric to define the affinity matrix, or first converting color-images into gray-level images and then use the
gray-level images to construct the affinity matrix (component-wise method). However, it is known that Euclidean
distances can not represent the color differences well and the component-wise method does not consider the correlation
between color channels. In this paper, we propose a new method to produce the affinity matrix, in which the color
images are first represented in quaternion form and then the similarities between color pixels are measured by quaternion
rotation (QR) mechanism. The experimental results show the superiority of the new method.
It is difficult to precisely detect all impulsive noise in color images due to the nonstationarity caused by edges and fine details. For many pixels, we can not absolutely classify them as noisy or noise-free, but can only describe them using the likelihood that they are corrupted by impulsive noise. Based on this consideration, we present a new filtering solution to removing impulsive noise from color images. The proposed method first utilizes the unit transforms of quaternions to represent the chromaticity difference of two color pixels, and then divides the image into noise-free and possible noisy pixels. Finally it performs adaptive weighted vector median filtering operations on only the possible noisy pixels to suppress noise. The new weighting mechanism is based on a joint spatial/quaternion-chromaticity criterion, which ensures that pixels with different contamination likelihoods have different contributions to the filter's output. The extensive simulation results indicate that the proposed method significantly outperforms some other well-known multichannel filtering techniques.
We present a new impulsive noise removal method, which combines a switching mechanism and adaptive weighted median filtering techniques. By utilizing four Laplacian operators and median-based comparison techniques to classify the image pixels into thin-line pixels, noise-free pixels, and noisy ones, the developed solution applies adaptive weighted median filtering operations only in the detected noisy locations to suppress impulsive noise, and keeps the other pixels unchanged. The simulation results exhibit the excellent performance gains of the proposed solution in suppressing impulsive noise with different contamination ratios over other prior-art methods in terms of both objective measurements and visual image quality.
We propose and demonstrate a novel orthogonal optical labeling scheme based on 40-Gbit/s optical frequency-shift keying (FSK) payload and 2.5-Gbit/s intensity-modulated (IM) labeling. Using the technology of carrier-suppressed modulation and conversion of differential phase-shift keying to IM, only one light source is needed to generate the optical FSK signal. The system performance, including range of IM modulation depth, bit error ratio, and dispersion limitation, is carefully investigated by numerical simulation. With IM modulation depth of 0.4, the 40 Gbit/s FSK payload and 2.5-Gb/s IM label are transmitted over a 50-km standard single mode fiber (SMF) with 0.87 and 0.92 dB penalty and show immunity to input power range upto 11 and 15 dB, respectively. Optimal methods to improve the system performance are also proposed and discussed. After optimization, the IM modulation depth can be reduced to 0.2.
We propose a novel scheme of high bit rate optical frequency
shift-keying transmitter. Base on the periodic notch spectral
properties of Mach-Zehnder delay interferometer and the carrier suppressing functionality of Mach-Zehnder modulator, a
high-speed optical FSK signal can be simply generated with another phase modulator and a single wavelength laser source.
The transmission characteristics of this FSK signal are investigated under varying dispersion management. Simulated
results show that 40Gb/s FSK signal gives only 1dB penalty after 80 km SMF transmission link under the
post-compensation management scheme.
Orthogonal ASK/DPSK labeling is a promising approach to ultra-high packet-rate routing and forwarding in the
optical layer. However, the limitation on the payload extinction ratio (ER) is a detrimental effect for the network
scalability and transparency. In this paper, we propose and experimentally demonstrate that mark insertion coding is an
efficient technique to improve the ER tolerance in optical orthogonal ASK/DPSK labeling scheme using an ASK
payload and a DPSK label. The experimental results show that by applying mark insertion coding to an orthogonally
labelled signal with an ASK payload up to 40 Gb/s and a 622 Mb/s or 2.5 Gb/s DPSK label, the tolerable payload
extinction ratio can be greatly increased up to 13 dB.
We experimentally demonstrate a novel decimal optical buffer scheme based on a multiloop configuration and a single switch element—an optical crosspoint switch (OXS) matrix. Its variable-delay range is of 1 to 999 times the basic delay unit. The buffer dynamic reconfiguration can be achieved at nanosecond switching speed. Our results show that by using a differential phase-shift keying (DPSK) payload in the buffer it can outperform an on-off keying payload with 4-dB sensitivity improvement owing to its alleviation of patterning-induced degradation, clearly validating DPSK as a promising modulation format to overcome nonlinear impairments and to extend number of hops in all-optical packet-switching network.
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