An effective approach to measure image motion is presented based on joint transform correlator(JTC), in order to measure the sub-pixel image motion caused by satellite attitude instability or vibration. Firstly, the high-speed CCD is used to capture image sequences, which are preprocessed by wavelet edge detection. Next the acquired image edge sequences are optically calculated by JTC, and an improved correlation peak is obtained. Lastly a modified centroid algorithm is proposed to get more accurate motion measurement. Motion measurement based on optical correlation is discussed, and the optical experiment system is also set up. The experimental results show that the measurement error is as low as 0.02 pixels, the accuracy is improved greatly.
It is difficult to dectect and recognize moving target for optical correlator owing to the image information containing various rotation and scale variation, though optical processing owns the advantage of high-speed, large capacity and real-time. An efficient approach was proposed to impove correlation peak and enhance recognition performance of target based on Fourier-Mellin transform, by which optical correlator is not sensitive to the distortion of image information, and it will alleviate greatly the complexity of image recognition. We have also constructed an detection and recognition system based on optical joint correlator, the computer simulations and experimental results show that the proposed method has got sharp corrlation peak and improved the detection performance.
To restore the motion blurred image caused by various vibration and attitude variation in remote
imaging, an approach is presented which is based on joint transform correlator (JTC). An auxiliary
high-speed CCD is used to capture image sequences When the prime CCD is imaging in exposure
period, these image sequences are optically calculated by JTC system, and image motion vector can be
effectively detected and point spread function is accurately modeled instantaneously, it will alleviate
greatly the complexity of image restoration algorithm. Finally, a simple restoration algorithm is
proposed to restore the blurred image. We have also constructed an image restoration system based on
joint transform correlator. The experimental results show that the proposed method has improved
image quality greatly.
Unmanned aerial vehicle remote sensing (UAVRS) is lower in cost, flexible on task arrangement and automatic and
intelligent in application, it has been used widely for mapping, surveillance, reconnaissance and city planning. Airborne
remote sensing missions require sensors with both high resolution and large fields of view, large format CCD digital
airborne imaging systems are now a reality. A refractive system was designed to meet the requirements with the help of
code V software, It has a focal length of 150mm, F number of 5.6, waveband of 0.45~0.7um, and field of view reaches
20°. It is shown that the value of modulation transfer function is higher than 0.5 at 55lp/mm, distortion is less than
0.1%, image quality reaches the diffraction limit. The system with large format CCD and wide field can satisfy the
demand of the wide ground overlay area and high resolution. The optical system with simpler structure, smaller size and
lighter weight, can be used in airborne remote sensing.
Thermal effect of optical system is the key factor influencing high resolution image quality for airborne CCD camera,
athermalization is the key technology and leading topic in optical engineering field. The researh field focus on infrared
system, however, the visible system is quite few considered. Based on optical compensation method, the conception of
general zoom system was proposed to realize athermal design for complex visible refractive system. Three steps of the
athermalization was considered as three status of zoom system design, correspondence between the athermal design and
zoom system design was established. Firstly a good optical system was designed to satisfy image quality in normal
temperature, and then multiple zooming positions were established in actual temperature range from -40°<i>C</i> to +60°<i>C</i> , the excellent imaging quality was obtained by replacing partial materials properly. An optical system in the 0.43um, 0.75um waveband was designed with 650mm focal length, F/5.6 F-number, 5.5° field-of-view by the general zoom method. The results showed the image quality had a reliable performance with -40°<i>C</i> +60°<i>C</i>, and the MTF is higher than 0.5 at the spatial frequency of 70lp/mm, image quality reached the diffraction limit. The MTF decreased only with 5%, the athermal design can meet high resolution requirement for airborne CCD camera in wide temperature range. The
atheraml research for visible optical system will further complete athermal theories and technologies, and its study and
applications will produce important value for military airborne optical system and space optical system.
Semiconductor laser is paid more attention and widely used in laser range finder, laser fuse and laser guidance due to its
monochromaticity, coherence and high density, as well as small volume and low power consumption. The principle of
laser encoding and emitting system is set forth. Based on the principle of spatial frequency-encoding, a laser encoding-emitting
system is developed; a new laser encoding mode is designed, which can transfer continuous laser into pulse
laser with different frequencies, they represent different position. The mathematic model to calculate the deviation from
center is obtained. A new encoding pattern is designed, which is composed of two light paths crossed 90°. Azimuth
information of target is given in orthogonal coordinate system and deviation from center is linearity. As well as,
characteristic distribution of spatial laser field is analyzed and irradiance distribution is homogeneous. Laser diode is
directly applied as guidance source and information carrier in place of solid-state laser. Output power of a single laser
diode can reach 3w. Two laser diodes are installed in series for increasing output power in the system. Tested in 2
kilometers outdoor; experimental results prove that: the receiver can receive correctly the signal emitted by system. The
laser encoding mode can satisfy guidance precision demand.
Multi-spectrum and high spatial resolution is the vital problem for optical design of aerial photogrammetric camera all the time. It is difficult to obtain an outstanding optical system with high modulation transfer function (MTF) as a result of wide band. At the same time, for acquiring high qualified image, chromatic distortion in optical system must be expected to be controlled below 0.5 pixels; it is a trouble thing because of wide field and multi-spectrum. In this paper, MTF and band of the system are analyzed. A Russar type photogrammetric objective is chosen as the basic optical structure. A novel optical system is presented to solve the problem. The new optical photogrammetric system, which consists of panchromatic optical system and chromatic optical system, is designed. The panchromatic optical system, which can obtain panchromatic image, makes up of a 9k×9k large format CCD and high-accuracy photographic objective len, its focal length is 69.83mm, field angle is 60°×60°, the size of CCD pixels is 8.75um×8.75um, spectral scope is from 0.43um to 0.74um, modulation transfer function is all above 0.4 in whole field when spatial frequency is at 60lp/mm, distortion is less than 0.007%. In a chromatic optical system, three 2k×2k array CCDs combine individually three same photographic objectives, the high resolution chromatic image is acquired by the synthesis of red, green, blue image data information delivered by three CCD sensors. For the chromatic system, their focal length is 24.83mm and they have the same spectral range of 0.39um to 0.74um. A difference is that they are coated in different film on their protect glass. The pixel number is 2048 × 2048; its MTF exceeds 0.4 in full field when spatial frequency is 30lp/mm. The advantages of digital aerial photogrammetric camera comparison with traditional film camera are described. It is considered that the two development trends on digital aerial photogrammetric camera are high-spectral resolution and high-spatial resolution. Merits of the aerial photogrammetric camera are multi-spectral, high resolution, low distortion and light-weight and wide field. It can apply in aerial photography and remote sense in place of traditional film camera. After put on trial and analyzing from the design results, the system can meet large scale aerial survey.