In this paper, a color transfer technique based on Adaptive Directional Wavelet Transform with Quincunx Sampling
(ADWQS) is proposed to transfer color from a color reference image to a grayscale target image. Due to ADWQS's
directional selectivity and symmetrical characteristic, the proposed scheme yields the best color transfer performance.
We search the best matching only in LL subband of luminance coefficients of the two images and then transfer the
chromaticity coefficients to corresponding positions. This operation greatly accelerates the colorization process and
meanwhile maintains the good performance. In addition, the proposed method has no constraint on the image size, i.e.,
the color reference image and the grayscale target image can be of different sizes.
Laser diodes are widely used in many fields, but the poor beam quality is an obvious deficiency. The intensity
distribution of a beam from a laser diode in the slow axis is so complex that it is difficult to be described by a Gaussian
distribution of a certain order. The beam qualities of a certain type of laser diode in the directions of perpendicular and
parallel to junction are evaluated in this paper. The intensity distributions in two directions are described respectively by
fundamental mode Gaussian distribution and multi-mode Hermite-Gaussian distribution. The computed data is basically
in accord with the experimental data. The mathematical model may provide some suggestions for the designing of optical
system with laser diodes and related simulations.
With the development of VLSI, CMOS image sensor has developed increasingly. The history of CMOS image sensor
was introduced, on the basis of analyzing the principle of CCD and CMOS image sensor, the advantages of CMOS
image sensor was summarized. The current research status and commercial productions of different companies were
described in this paper, moreover, the technical specifications were presented. At last, the current applications and trends
of CMOS image sensor was focused.
Discrete wavelet transform is an effective tool to generate scalable stream, but it cannot efficiently represent edges which are not aligned in horizontal or vertical directions, while natural images often contain rich edges and textures of this kind. Hence, recently, intensive research has been focused particularly on the directional wavelets which can effectively represent directional attributes of images. Specifically, there are two categories of directional wavelets: redundant wavelets (RW) and adaptive directional wavelets (ADW). One representative redundant wavelet is the dual-tree discrete wavelet transform (DDWT), while adaptive directional wavelets can be further categorized into two types: with or without side information. In this paper, we briefly introduce directional wavelets and compare their directional bases and image compression performances.
A 2.1 km terrestrial free-space optical data link operating at 5 Gbps by using WDM and 1550 nm fiber communication techniques was established. Two 2.5 Gbps pattern generators are used to directly modulate 1530 nm and 1550 nm DFB lasers respectively. The output of each modulated optical signal are combined by a CWDM, and then amplified by a 20dBm EDFA. The amplified optical signal is then applied to a specially designed transmitting telescope. The received optical signal is focused onto the core of a 62.5μm multi-mode optical fiber using coupling optics within the receive telescope. The coupled optical signal is interfaced to a de-multiplexer to separate the two individual wavelengths, where each of two outputs is then connected to a 2.5 Gbps receiver. The BER and optical stability measurements are presented to quantify and demonstrate link quality for a 2.1 km span. BER and received optical coupled power data is presented to illustrate atmospheric effects associated with typical link performance.
As the effects of various weather conditions on laser beams propagating in the atmosphere are hard to mitigate, in order to obtain high quality of the laser propagation, a new method is put forward in this paper. The theory uses feedback compensation technology to mitigate atmospheric scintillation effect, namely collecting the atmospheric turbulence factor in real time, and feedback it to the transmitter of laser real-timely. An experiment and simulation tests to verify the effect of feedback compensation have been taken to analyze the feedback effects and feasibility. The obtained results show the method can mitigate atmospheric scintillation in the atmospheric transmission.