Laser range-gated imaging is one of the effective techniques of underwater optical imaging. It could make the viewing distance up to 4 to 7 times with the video image processing technology. Accordingly, the control and image processing technologies come to be the key technologies for the underwater laser range-gated imaging system. In this article, the integrated platform of controlling and digital video processing for the underwater range-gated laser imaging system based on FPGA has been introduced. It accomplishes both the communication for remote control system as the role of lower computer and the task of high-speed images grabbing and video enhance processing as the role of high-speed image processing platform. The host computer can send commands composed to the FPGA, vectoring the underwater range-gated laser imaging system to executive operation.
Binocular stereo vision is a common passive ranging method, which directly simulates the approach of human visual. It
can flexibly measure the stereo information in a complex condition. However there is a problem that binocular vision
ranging accuracy is not high , one of the reasons is the low precision of the stereo image pairs matching . In this paper,
based on trinocular vision imaging ranging algorithm of constraint matching, we use trinocular visual ranging system
which is composed of three parallel placed cameras to image and achieve distance measurement of the target. we use
calibration method of Zhang to calibrate the cameras, firstly, the three cameras are calibrated respectively, then using the
results to get three groups binocular calibration. Thereby the relative position information of each camera are obtained.
The using of the information obtained by the third camera can reduce ambiguity of corresponding points matching in a
Binocular camera system. limiting search space by the epipolar constraint and improve the matching speed, filtering
the distance information , eliminate interference information which brings by the feature points on the prospect and
background to obtain a more accurate distance result of target. Experimental results show that, this method can overcome
the limitations of binocular vision ranging , effectively improving the range accuracy.
Color fusion technology, one of the typical technologies, has been emphasized all over the world. Multiband images are
fused into a color image. Some effective visible and thermal infrared color fusion algorithms have been proposed now.
We have successfully run a real-time natural sense of visible/infrared color fusion algorithm in DSP and FPGA hardware
processing platforms. However, according to different needs, gray image fusion technology has its own unique
Based on the natural sense of color image fusion algorithm of the visible and infrared, we have proposed a visible /
infrared gray image fusion algorithm. Firstly we do a YUV color fusion. Then we output the brightness of the fusion as
gray fusion images. This algorithm for image fusion is compared with typical fusion algorithms: the weighted average,
the Laplace Pyramid and the Haar basis wavelet. Several objective evaluation indicators are selected. The results of
objective and subjective comparison show that the algorithm has most advantages. It shows that multiband gray image
fusion in the color space is available.
The algorithm is implemented on a DSP hardware image processing platform real-time with the TI's chip as the kernel
processor. It makes natural sense of color fusion and gray fusion for visible light (low level light) and thermal imaging
integrated. Users are convenient to choose model of the natural sense of color fusion or gray fusion for real-time video
Based on the radiation transmission theory, a model of backscattering light and signal light for atmospheric range-gated imaging system has been developed. This model gives time dependent irradiance of backscattering light and signal light on photocathode during the propagation of illuminating pulsed laser in atmosphere. The model could be used to predict and optimize parameters of range-gated imaging systems. Examples with typical system parameters under fog conditions are computed with this model. The results can lead to several conclusions. The first one is that the photocathode irradiance of object image could be higher than that of the background even if optical signal power is lower than optical backscattering power. The second one is that increase in peak power of illumination laser could not improve the image contrast between an object and its background. The last one is that image contrast could be improved by reducing laser pulse width while keeping average laser power unvaried, reducing sensors’ field-of-view, or increasing the separation between transmitter and receiver.