| For illuminant design,it’s not only to provide bright enough vision,but satisfy human’s variable visual task requirements.Traditional light source was changed from daylight,candle,bulb to fluorescent,which improves the stability,efficiency and CCT alterable,respectively.To spectrum adjustable,it will be the core novety of the ’Fifth Generation’ illuminant design.With spectrum optimization in different working environment,people can be provided with better visual experience.The aim of dissertation is to establish a spectrally controllable lighting environment system and to reveal visual and cognitive performance of LED lighting on people in professional spaces.To reach this aim,this project concentrates on two goals:(1)Visual Perception:study of the visual effects of LED lighting to provide evidence of benefits for hospital with the optimization of color rendering and local contrast enhancement.(2)System Design:design and system integration of an accurately controllable lighting environment in an indoor space with tunable spectrum,light intensity,color temperature.In the visual perception study,we proposed two models to optimize LED lighting spectrum in operation room with hemoglobin(HGB)model and spectral reflectance comparison(SRC)model.The new methodology is specifically developed to enhance luminance contrast based on a spectral comparison that is valid for the entire visible light band.Entropy evaluation method specifically for visual enhancement is created to value images of samples under different lighting conditions.Results showed that light with optimal spectrum achieved higher contrast than commercial white light in different color temperatures.Based on the gray value entropy,color entropy was proposed because people mostly observed the objects with color information rather than seeing monochromatic images.To verify the effectiveness of our method,spatial frequency analysis is adopted.However,the limitation of those two methods is that they were all manipulated on the ’image’,whereas visual task is mostly completed by human’ directly eye-watching.So visual entropy evaluation based on the human visual system was proposed then.Additionally,color entropy is one-dimension entropy of color intensity distribution while visual entropy is two-dimension entropy of color clustering distribution with additional evaluation of the object spatial distribution.Thus,visual entropy proposed provided more accurate evaluation of the details that tissues presented.To the system design,based on the entropy theory,a LED surgical lighting system with splecturm flexibly adjusted was built.Optical design is the most complicated and important part in the whole project.It has a direct influence on the lighting effect.To realize the ’flexible’illuminating target,specific lighting system is designed and built,with lens design,disk distribution design,manufacturing and so on.Many efforts have been done and several outcomes were got in different stages.Based on the research study and hospital interview,we provided four optical design plans.After the comparison of four plans proposed,we finally choose the disk lighting in our project.According to the optical design and mechanical design,the first version demo disk was made out.Based on the lighting system V1,the system V2 was built with higher mechanical compactness.The lighting disk size is only 2/3 of the V1.Meanwhile,the heat sink has also been optimized with more flexibility of angle adjustment and smaller space occupied.The total weight is 1/2 of the original one.The final four-disk system is a combination of four lighting system V2 added with the mechanical holding structure.Our lighting system had also been pilot used in three top hospitals.According to the surgeons,feedback,most of them are excited to see the LED white light with flexible spectrum because they have been tired of the traditional halogen light.Tissue contrast enhancement is indeed a great attraction to them because it can do a big favor in operation. |
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