【正文】 尋，因而人眼的結(jié)構(gòu)特征和視覺特性是值得關(guān)注的。視覺增強(qiáng)系統(tǒng)應(yīng)用機(jī)器視覺設(shè)備和技術(shù)增強(qiáng)和擴(kuò)展了人眼的視覺。在過去幾年，中國的海上搜救組織發(fā)生了很大的變化，體現(xiàn)在參與了國際上搜救的合作和采用了先進(jìn)的技術(shù)。中國政府和海事部門非常重視研究和發(fā)展海上搜救技術(shù)。 human vision characteristics。本文針對搜救環(huán)境中人眼觀測的弱點(diǎn)，提出了基于可見光成像系統(tǒng)和紅外成像系統(tǒng)的視覺增強(qiáng)系統(tǒng)進(jìn)行海上搜救的方案，給出了系統(tǒng)框圖。該系統(tǒng)輔助搜救人員進(jìn)行搜救，將提高海上目標(biāo)尤其是弱小目標(biāo)探測的靈敏度和發(fā)現(xiàn)率，能夠有效地挽救人民的生命和財(cái)產(chǎn)，具有巨大的經(jīng)濟(jì)效益和社會作用。 target detection1 引言隨著航運(yùn)業(yè)的發(fā)展,我國水上交通安全保障和應(yīng)急搜救任務(wù)日益繁重?！秶抑虚L期科學(xué)和技術(shù)發(fā)展規(guī)劃綱要》指出：“重點(diǎn)開發(fā)交通事故預(yù)防預(yù)警、應(yīng)急處理技術(shù)，開發(fā)運(yùn)輸工具主動與被動安全技術(shù)，交通運(yùn)輸事故再現(xiàn)技術(shù)，交通應(yīng)急反應(yīng)系統(tǒng)和快速搜救等技術(shù)。然而，現(xiàn)有的海上救助搜尋方法，尤其是搜索人，主要借助人眼進(jìn)行搜尋。它是智能交通和交通安全領(lǐng)域的重要前沿基礎(chǔ)技術(shù)和研究熱點(diǎn)[13]，在汽車駕駛、飛機(jī)導(dǎo)航等方面得到較為廣泛的應(yīng)用[46]，尤其在不利天氣或夜間駕駛和飛行時(shí)有效增強(qiáng)了人的視覺，在保障交通安全方面起到良好的作用[79]。 人眼結(jié)構(gòu)圖1 人眼結(jié)構(gòu)圖人眼結(jié)構(gòu)圖如圖1所示。在0186。是用于看近處物體的。錐狀細(xì)胞是一種明視覺器官，只有在明亮條件下它才起作用，但卻能夠分辨顏色和細(xì)節(jié)。)。除此區(qū)域外，分布情況基本上是關(guān)于中央凹對稱的。人眼有視覺暫留現(xiàn)象，當(dāng)兩種不同的色光間隔時(shí)間很短，先后對視網(wǎng)膜刺激，視網(wǎng)膜就分不出刺激的先后，只能產(chǎn)生一個(gè)總體的刺激知覺，這便是視覺的時(shí)間混色效應(yīng)。由此可以看出：a. 高斯型和指數(shù)型是低通濾波器；Barten 和復(fù)合模型是帶通濾波器，復(fù)合模型較Barten 模型向低頻移動；b. Barten模型和復(fù)合模型在大于15cyc/ ～ mrad 的高斯型曲線之間，而指數(shù)型則偏高；圖3 幾種人眼視覺的M T F 曲線c. 由于Barten 模型和復(fù)合模型的復(fù)雜性, 以往分析大都采用指數(shù)型或高斯型MTF模型；，這在搜救的復(fù)雜環(huán)境中，容易將弱小目標(biāo)抑制掉，不易搜索到小目標(biāo)。視覺增強(qiáng)系統(tǒng)，可以克服上述的缺陷和不足，并應(yīng)用于對水上船筏和遇險(xiǎn)人員的救助搜尋，可以提高救助搜尋的速度和準(zhǔn)確性，對提高救助的成功率和效率有重要作用。人眼觀測可見光成像系統(tǒng)紅外成像系統(tǒng)目標(biāo)檢測目標(biāo)檢測圖像融合場景標(biāo)注搜救人員決策海面環(huán)境圖4海上搜救視覺增強(qiáng)系統(tǒng)結(jié)構(gòu)框圖在搜救過程中，由可見光成像和紅外成像系統(tǒng)組成機(jī)器視覺系統(tǒng)，搜尋目標(biāo)時(shí)輔助人眼進(jìn)行觀測并克服了視覺系統(tǒng)的生理缺陷。5結(jié)論由于人眼視覺的限制，研究先進(jìn)的技術(shù)提高海上搜救性能是必要的。ping University, V229。m, K., Aspects of Vision Enhancement Systems in cars based on infrared imaging. Acreoreport, No acr003758. 2000.[5] E. Hollnagel, Effects of a night vision enhancement system (NVES) on driving: Results from a simulator study, The Second International Driving Symposium on Human Factors in Driver Assessment, Training and Vehicle Design, 2003. [6] F. Sadjadi, M. Helgeson, J. Radke and G. Stein, Enhanced vision for adverse weather aircraft landing, International Journal of Infrared and Millimeter Waves 17 (1996), no. 1, 150.[7] Nilsson, L. amp。ping University.[9] Gish, K. (2001). Driving Behaviour and Performance using an infrared Night Vision Enhancement System. Final report. Transportation Safety Division, PA: USA.[10]J. K. Caird, W. J. Horrey and C. J. Edwards, Effects of conformal and nonconformal vision enhancement systems on olderdriver performance, vol. 1759 2001.[11]R. C. Peterson, J. S. Wolffsohn, M. Rubinstein and J. Lowe, Benefits of electronic vision enhancement systems (EVES) for the visually impaired, American Journal of Ophthalmology 136 (2003), no. 6, 11291135.[12]Blair ,Steven ,Charies ,Mounting/adjusting mechanism for vision enhancement system,US Patent 20,2007.[13]周燕，金偉其. . 2002. Vol128. No11:5759,62[14]Lloyd J M. Thermal imaging system. 尹白云等譯,北京: 國防工業(yè)出版社, 1981) .[15]Ratches J A l. Night vision laboratory static performance model for thermal viewing systems[ R] . U. S. Army Electronics Command , Report No1 ECOM 7043 , 1975[16] Barten P GJ. The SQRI method : a new method for the evaluation of visible resolution on a display [J ] , Proc1 Soc1 Inf1 Dispel , 1987 ,28 :253 —262[17]Jacobson RE. An evaluation of image quality metrics, The journal of photographic science , 1995 ,43 : 7 —16Vision Enhancement System for Maritime Search and RescueSHI Chaojian, XU Kaiyu, XIAO Baojia and MO Jianying Shanghai Maritime UniversityAbstract Because of the limitation of physiological characteristics of human eyes, it is necessary to develop vision enhancement system for maritime search and rescue (SARVES),which improve the poor searching performance of human vision at sea. A system with its framework based on the visible light imaging system and infrared imaging system is proposed in the paper to pensate the weakness of the human observation in the maritime search and rescue environment. The system will promote the sensitivity and the detection rate of targets, especially small ones, at sea, ensure the safety of life and reduce economical losses in marine accidents.Keywordsvision enhancement system。 position. A larger area, 2186。 off axis and then decrease in density out to the extreme periphery of the retina.Fig. 2 Distribution of rods and cones in the retina Human visionThe perception caused by the external light radiating into the human eyes to stimulate the retina is called vision. Vision is a plex physiological process. External light is focused on the retina through cornea, iris and lens, and stimulates photosensory cell to generate nerve pulse, which is transmitted to the brain through vision nerve to produce vision. Because of the visual temporary retaining phenomenon of human eyes, when the interval of two different lights is very short, the retina can’t distinguish the order of the stimulation by the lights. It only produces a total stimulation perception, causing the vision’s time blending effect. Besides, human eyes also have a limited distinguishing ability, when the minimal region of the retina is stimulated by two different lights at the same time, the retina can’t distinguish two stimulations in the minimal region, only produce total stimulation perception, which causes vision’s space blending effect.Fig. 3. A few MTF curves of the human visionSeveral typical frequency response models have been introduced to represent the characteristics of human visual systems [1317], ., exponent model, Gauss model, Barten model and pound model, which are illustrated in Fig. 3 by curves of modulation transfer function (MTF). From theses curves, it can be noted that,? Gauss model and exponent model are lowpass filters, while Barten model and pound model are bandpass filter. Compared to Barten model, pound model is inclined to low frequency.? When the region is greater than 15 cyc/deg, Barten model and pound model are generally located between mrad gauss model curve and mrad one, but the exponent one is much higher.? Because of the plexity of Barten model and pound model, exponent MTF model or gauss MTF model is mostly used in the previous analysis.? Modulation transfer function response of human visual characteristic is nonuniform in the above visual models. This can easily inhibit the smal