推掃式遙感相機(jī)對焦評價方法研究
發(fā)布時間：2019-01-27 10:52
【摘要】：遙感成像技術(shù)在國民經(jīng)濟(jì)與國家安全領(lǐng)域起著極為重要的作用,而遙感器作為遙感技術(shù)中的核心一直是重點研究的對象。當(dāng)前,基于TDICCD的推掃式遙感相機(jī)作為遙感器的一種,在航天遙感技術(shù)中越發(fā)顯示出其重要性。由于空間環(huán)境的影響,遙感相機(jī)往往會發(fā)生離焦,因而為了獲取高質(zhì)量圖像,需要進(jìn)行有效的自動對焦技術(shù)。而推掃式遙感相機(jī)由于其成像的特殊性,使得其在任意時刻所拍攝到的景物都不同,從而需要根據(jù)其特點提出一種與攝影目標(biāo)景物無關(guān)的對焦評價方法,繼而用于推掃式遙感相機(jī)自動對焦當(dāng)中。 針對上述背景,本文介紹了TDICCD推掃式遙感相機(jī)成像機(jī)理,并對目前可用于推掃式遙感相機(jī)的對焦評價方法進(jìn)行了分析,從而在此基礎(chǔ)上分別從小波包域與空間域提出了兩種與攝影目標(biāo)景物無關(guān)的對焦評價方法——基于小波包能量譜的對焦評價方法與基于強(qiáng)邊緣寬度直方圖的對焦評價方法。 在基于小波包能量譜的方法中,本文先是介紹了小波包技術(shù)具有頻率分解精細(xì)、時頻特性良好的技術(shù)特點,并借鑒功率譜一致性的理論,發(fā)現(xiàn)不同內(nèi)容圖像間在小波包域具有幾乎一致的能量譜曲線,從而建立了基于小波包能量譜不變性的觀點。算法先是對圖像進(jìn)行小波包分解,接著選取與相機(jī)運動方向相垂直的不同頻率下的小波包系數(shù),繼而對這些小波包系數(shù)進(jìn)行處理得到相應(yīng)頻率下的能量表征,最終對各頻率下的能量進(jìn)行加權(quán)求和得到清晰度評價值,從而指導(dǎo)相機(jī)調(diào)焦。通過仿真實驗與實拍實驗發(fā)現(xiàn)：該對焦評價方法在無像移失配或在有像移失配但離焦模糊不是過大的情況下可做到與攝影目標(biāo)景物無關(guān)的絕對式檢焦。 在基于強(qiáng)邊緣寬度直方圖的方法中,本文以遙感圖像大多具有直線結(jié)構(gòu)為依據(jù),根據(jù)模糊會引起邊緣擴(kuò)散為指導(dǎo),從而以邊緣的擴(kuò)散情況來表征圖像清晰度。算法先是通過邊緣檢測算子選取與相機(jī)運動方向平行的強(qiáng)邊緣,由強(qiáng)邊緣垂直方向的灰度變化計算其邊緣寬度,之后對所有的強(qiáng)邊緣寬度建立直方圖,繼而引入基于直方圖信息的距離因子,針對不同寬度的邊緣加入不同的權(quán)重,最終求和得到清晰度評價值,從而指導(dǎo)相機(jī)調(diào)焦。通過實拍實驗與模糊圖像庫的測試發(fā)現(xiàn)：該對焦評價方法具有與攝影目標(biāo)景物無關(guān)的絕對式檢焦特點,對焦曲線擁有良好的單調(diào)性,并不受像移失配的干擾,還具有與主觀評價一致性的特點,是一種較為有效的推掃式遙感相機(jī)對焦評價方法。
[Abstract]:Remote sensing imaging technology plays an important role in the field of national economy and national security, and remote sensor as the core of remote sensing technology has been the focus of research. At present, push-sweep remote sensing camera based on TDICCD, as a kind of remote sensor, has become more and more important in space remote sensing technology. Because of the influence of space environment, remote sensing camera will often defocus, so in order to obtain high quality image, it is necessary to carry out effective automatic focusing technology. Because of the particularity of its imaging, the push-scan remote sensing camera has different scene at any time, so it is necessary to put forward a focusing evaluation method which is independent of the target scene according to its characteristics. It is then used in automatic focusing of push-sweep remote sensing camera. In view of the above background, this paper introduces the imaging mechanism of TDICCD push-scan remote sensing camera, and analyzes the focusing evaluation method which can be used for push-scan remote sensing camera. On the basis of this, two methods of focusing evaluation independent of the object of photography are proposed from the wavelet packet domain and the spatial domain, namely, the focus evaluation method based on wavelet packet energy spectrum and the focus evaluation method based on the strong edge width histogram. In the method based on wavelet packet energy spectrum, this paper first introduces that wavelet packet technology has the characteristics of fine frequency decomposition and good time-frequency characteristic, and draws lessons from the theory of power spectrum consistency. It is found that there are almost consistent energy spectrum curves between different content images in wavelet packet domain, thus the viewpoint of energy spectrum invariance based on wavelet packet is established. The algorithm firstly decomposes the image with wavelet packet, then selects the wavelet packet coefficients at different frequencies perpendicular to the camera motion direction, and then processes these wavelet packet coefficients to obtain the energy representation at the corresponding frequency. Finally, the weighted summation of the energy at each frequency is used to obtain the definition evaluation value, which can guide the camera to focus. Through the simulation experiment and the real film experiment, it is found that the method can achieve absolute focus detection without image shift mismatch or without image shift mismatch, but the defocus blur is not too large, which has nothing to do with the object of photography. In the method based on strong edge width histogram, this paper is based on the fact that most remote sensing images have straight line structure, which is guided by the edge diffusion caused by blur, so that the image clarity can be represented by the edge diffusion. The algorithm firstly selects the strong edge parallel to the camera's moving direction through edge detection operator, calculates the edge width from the gray level change in the vertical direction of the strong edge, and then establishes the histogram for all the strong edge widths. Then the distance factor based on histogram information is introduced, and different weights are added to the edges of different widths, and the definition evaluation value is obtained by summing up, thus guiding the camera focusing. It is found that the method has the characteristics of absolute focus detection independent of the object of photography, the focus curve has a good monotonicity and is not disturbed by the image mismatch, through the experiments of real time shooting and the test of fuzzy image database, the results show that the method of focusing evaluation has the characteristics of absolute focus detection independent of the object of photography, and the focus curve has good monotonicity. It is also consistent with subjective evaluation and is a more effective method for focusing evaluation of push-sweep remote sensing camera.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TP73
本文編號：2416189
[Abstract]:Remote sensing imaging technology plays an important role in the field of national economy and national security, and remote sensor as the core of remote sensing technology has been the focus of research. At present, push-sweep remote sensing camera based on TDICCD, as a kind of remote sensor, has become more and more important in space remote sensing technology. Because of the influence of space environment, remote sensing camera will often defocus, so in order to obtain high quality image, it is necessary to carry out effective automatic focusing technology. Because of the particularity of its imaging, the push-scan remote sensing camera has different scene at any time, so it is necessary to put forward a focusing evaluation method which is independent of the target scene according to its characteristics. It is then used in automatic focusing of push-sweep remote sensing camera. In view of the above background, this paper introduces the imaging mechanism of TDICCD push-scan remote sensing camera, and analyzes the focusing evaluation method which can be used for push-scan remote sensing camera. On the basis of this, two methods of focusing evaluation independent of the object of photography are proposed from the wavelet packet domain and the spatial domain, namely, the focus evaluation method based on wavelet packet energy spectrum and the focus evaluation method based on the strong edge width histogram. In the method based on wavelet packet energy spectrum, this paper first introduces that wavelet packet technology has the characteristics of fine frequency decomposition and good time-frequency characteristic, and draws lessons from the theory of power spectrum consistency. It is found that there are almost consistent energy spectrum curves between different content images in wavelet packet domain, thus the viewpoint of energy spectrum invariance based on wavelet packet is established. The algorithm firstly decomposes the image with wavelet packet, then selects the wavelet packet coefficients at different frequencies perpendicular to the camera motion direction, and then processes these wavelet packet coefficients to obtain the energy representation at the corresponding frequency. Finally, the weighted summation of the energy at each frequency is used to obtain the definition evaluation value, which can guide the camera to focus. Through the simulation experiment and the real film experiment, it is found that the method can achieve absolute focus detection without image shift mismatch or without image shift mismatch, but the defocus blur is not too large, which has nothing to do with the object of photography. In the method based on strong edge width histogram, this paper is based on the fact that most remote sensing images have straight line structure, which is guided by the edge diffusion caused by blur, so that the image clarity can be represented by the edge diffusion. The algorithm firstly selects the strong edge parallel to the camera's moving direction through edge detection operator, calculates the edge width from the gray level change in the vertical direction of the strong edge, and then establishes the histogram for all the strong edge widths. Then the distance factor based on histogram information is introduced, and different weights are added to the edges of different widths, and the definition evaluation value is obtained by summing up, thus guiding the camera focusing. It is found that the method has the characteristics of absolute focus detection independent of the object of photography, the focus curve has a good monotonicity and is not disturbed by the image mismatch, through the experiments of real time shooting and the test of fuzzy image database, the results show that the method of focusing evaluation has the characteristics of absolute focus detection independent of the object of photography, and the focus curve has good monotonicity. It is also consistent with subjective evaluation and is a more effective method for focusing evaluation of push-sweep remote sensing camera.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TP73
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