Weiqi Jin

Real-time color transfer system for low-light level visible and infrared images in YUV color space

A real-time color transfer system based on 3 pieces of multi-media DSP TM1300 for low-light level visible(LLLV) and infrared(IR) images is built. Computing quantity is split among three TM13003. Two pieces of TM1300 preprocess the dual-band images and calculate their mean and standard deviation respectively. The third TM1300 executes fusion and color transfer in YUV space: Firstly the two preprocessed images are fused into one primary color image(source image) in which hot targets present warm color, cold targets present cool color. Then the mean and standard deviation of source images in Y, U, V components are deduced by preprocessed images pixel value and their mean and standard deviation. Finally, the Y, U and V component of source image are scale by the variation ratio of a day-time color image(target image) to the source image. The color and luminance distribution of the target image is transferred into source image and makes it present a sort of day-time color appearance. Comparing to the usually used l&agr;&bgr; space, color transfer in YUV space can avoid iterative color space transformation, logarithmic and exponential calculation, and thus be effective in real-time realization while the color transferred results are acceptable.

Contrast enhancement using non-overlapped sub-blocks and local histogram projection

Contrast enhancement regarded as a significant branch of image processing, not only enhances human perception of details hidden in the scene, but also improves the rapid recognition of interested targets. In this paper, a non-overlapped sub-blocks and local histogram projection based contrast enhancement (NOSHP) is presented. First, the original image is segmented into numbers of non-overlapped sub-blocks where the histogram projection (HP) is then executed individually. Subsequently, each sub-block is related to its adjacent three ones by certain weights, so that the integral image and local details can be both enhanced. Experiments in this paper approve that NOSHP can effectively enhance the local details as well as properly preserve the image brightness to avoid the annoying blocking effect and wash-out effect. Moreover, this algorithm can dramatically reduce the time consumption in practical use, leading to a useful real-time processing method well suited to the consumer electronic products.

Objective evaluation of color fusion of visual and IR imagery by measuring image contrast

Color night vision through fusion of images derived from visible and thermal infrared sensors has come into application. A lot of research of perceptual or subjective evaluation of color fusion algorithms is conducted by the TNO, MIT and NRL[1-5]. Objective evaluation is becoming an increasing issue. A good fusion algorithm should preserve or enhance all of the useful features, i.e., targets pop out and content or details from the source images. Objective: The goal of our research is to predict details and target detectability of color fusion images by measuring image contrast. Methods: A color image contrast metric[11], which was designed to compute how much details for natural images, is employed to measure details and target detectability of color fusion images in this paper. A sub-band contrast index is defined, the first band contrast index indicates the level of details, and higher band contrast indexes indicate the level of target detectability. Results: The perceptual details have high correlation with the first sub-band contrast indexes, and the perceptual target detectability has correlation with higher sub-band contrast indexes. This means the sub-band contrast indexes may predict details and target detectability, however, noise effect on details need to be considered and prediction of target detectability need to be improved.

Color fusion algorithm for visible and infrared images based on color transfer in YUV color space

Color fusion algorithm for visible and infrared(IR) images based on color transfer in YUV color space under trees, lawn, or land background is presented. Considering the red color will alert observers to possible interested target or danger, this paper aims at working on an algorithm that emphasizes hot targets in IR image with intense red, and the background details in visible image present natural color similar to a color day-time image. V component of YUV space represents the difference between red and Y. Properly increasing the V value will obtain intense red color. Therefore, a nonlinear transfer method based on local mean value of the IR image is proposed. A window of size 5x5 is used to locate hot target in IR image. When the local gray mean value in this window is larger than the global mean value, we determine that this pixel is in a hot area. Then its V value is increased by the ratio of the local gray mean value to the global mean value. Tests show that this method pops out the hot targets with intense red color while the background rendered natural color appearance.

Color fusion schemes for low-light CCD and infrared images of different properties

Although gray-level fused images can optimally integrate the modalities of low-light CCD and infrared imager, operators cannot tell from which modality the details originate. Thus the fundamental that human eyes can discern much more color categories than gray levels has been used to assigns a distinct color to each sensor modality. But the color fused image which has no natural appearance will fatigue operators greatly. Our approach is building on MIT scheme and aims at achieving natural appearance in the color fused image. MIT scheme derives its basis from biological models of color vision and utilizes the feed-forward center-surround shunting neural network to enhance and fuse low-light and infrared images. We bring forward linear fusion architecture, and composite architecture that comprises the enhancement part of MIT scheme and the linear fusion architecture. Furthermore, enhancement and combination methods for low-light and infrared images of different properties have been specified.

Color night vision based on color transfer in YUV color space

To obtain a color night vision image, we proposed a color transfer algorithm in YUV color space based on the color transfer algorithm in lαβ color space which Reinhard proposed. After rendering the simple statistics (means and standard deviations) of the target image to the source image, the color appearance of the target image is transferred to the source image. 2D chromatic histogram (UV histogram) which can help to find an appropriate target image is established. Finally, we illustrated several examples of color transfer to multi-band fused images which are fused in MIT fusion scheme. After a color fused image is obtained, the color transfer is executed to render the color information of the target image to the fusion image. The final image could have a day-like color appearance. Besides, the algorithm has less operation than which in lαβ color space because of less transform complexity. It can be realized in real time in digital signal processors without color space transformation between RGB and YUV.

Sub-pixel processing algorithm of the reducing boundary recursive error in staring FPA micro-scanning imaging

By analyzing the error distribution rule of the boundary recursive reconstruction algorithm in controlled micro-scanning, a sub-pixel image processing algorithm is proposed to reduce the error. The gray statistical principle is used in the algorithm to optimize the error and acquire the sub-pixel image that approximates the original image. The simulation result shows that the eect of this algorithm is better than the over-sample and simple boundary recursive algorithm (BRA), and it results in a good effect both in those of visible light and infrared imaging systems. Therefore, the application of this algorithm will enhance the performance of optoelectronic imaging systems.

Speckle noise suppression of range gated underwater imaging system

Images associated with underwater imaging systems are normally degraded by the intervening water medium. The imaging instrument records not only the signal of interest, i.e., the radiance diffusely reflected from underwater target, but also the radiance scattered into the field of view by water molecule and particulates. In order to improve the system performance, range gated underwater imaging system is used to enhance image quality and visibility in turbid conditions. Range gated imaging utilizes time discrimination to improve signal-to-backscattering noise ratio by rejecting backscattered light from the medium. The range gated underwater imaging system basically consists of a pulsed laser system, a control and synchronous logics and a high-speed gated camera. Because a laser is a highly coherent light source, speckle noise results from the randomly constructive or destructive interference of the scattered light rays will appear in the images obtained from the range gated underwater imaging system. The random granular speckle noise brings great difficulty for the image processing. So the formation causes of speckle noise are discussed and several different material objects under standard light source and laser are chosen to carry out speckle noise comparative analysis. And a multidirectional morphological filtering algorithm for reducing speckle noise is proposed by using the characteristics of morphologys multi-resolution analysis and fast-computing. In order to evaluate the method objectively, equivalent number and speckle index are introduced. The experimental results demonstrate that the approach that is adopted not only can reduce the speckle noise of the image effectively but also can preserve the feature detail efficiently.

MRGC performance evaluation model of gas leak infrared imaging detection system

Gas leak infrared imaging detection technology has become one of the most effective means to detect gas leaks. We propose a novel MRGC (minimum resolvable gas concentration) model that is suitable for evaluating the performance of passive GLIIDSs (gas leak infrared imaging detection systems). An MRGC equivalent calculation method and a direct MRGC measurement method based on the MRTD (minimum resolvable temperature difference) model are also proposed. The MRGC measurement system is designed and built. The measured and calculated results are in good agreement, which verifies the MRGC models correctness and demonstrates the effectiveness of the MRGC performance evaluation method.

Range-gated underwater laser imaging system based on intensified gate imaging technology

The range-gated laser imaging technology can eliminate the backscattering noise and has a range of from 4 to 6 times that of a conventional camera with floodlights in the strongly scattering waters, which becomes a useful technique in oceanic research, deep-sea exploration, underwater remote control and robotic works. The characteristics of range-gated underwater laser imaging were analyzed in this paper, and the basic requirements for gated ICCD were presented. As a result, Gated Gen II+ Image Intensifier and progressive scanning CCD were assembled together to meet the requirements, which was called the Gate Intensified CCD camera. Combined with the small-sized programmable high voltage power supply, video image acquisition/control system and high power lamp-Pumped blue-green Nd:YAG pulse laser, the experimental system was developed. Experiments were carried out in pipes full of saturated salt water and large pools. When tested by USAF 1951 resolution target, the detecting range can extend to about 30 meters.