面向半导体照明的光学

Optics in Solid State Lighting

以发光二极管(LED)为核心的半导体照明光源成为世界公认的第三代照明光源。通常基于蓝光LED抽运黄色荧光粉产生白光的方案,因荧光粉的斯托克斯位移和宽光谱,其具有产业化价值的发光效率上升范围受到极大限制。另外,传统封装LED因其朗伯型发光分布和超高亮度会造成严重的眩光以及光分布难以满足照明应用要求从而导致光污染、光浪费,导致传统封装LED不能直接应用于通用照明领域。基于色度学原理,研究了半导体照明的极限流明效率,结果表明,基于红、绿、蓝三基色合成白光的方案,优化后在整个半导体照明白光区域显色指数Ra大于80,其极限流明效率可达430 lm/W,远远大于通常的蓝光LED与黄色荧光粉合成白光的方案。总结了在光学系统设计方面的系列成果:为使LED的配光满足应用要求,提出了基于分离变量的非成像光学系统设计理论以及为消除因光源的扩展性和法向矢量误差带来的照度分布偏移理想情况而引入的多种反馈迭代策略;面向道路照明,提出了按亮度设计自由曲面配光系统的方法,在保证照明参数满足标准的前提下,获得可实现最大的亮度/照度比的自由曲面光学系统;面向室内照明,利用非成像光学设计具有一体化微透镜结构的散光板,将类似于点光源的LED阵列转化为均匀柔和发光的面光源,大大降低了眩光,并引入模块化方案降低维修成本;面向特种照明,提出了由多个光学曲面构成的照度均匀的准直光学系统结构以及航标灯光源。

Solid state lighting sources based on white light emitting diodes（LEDs） are considered as the third generation lighting sources.Generally,white light is generated by combination of the blue LEDs and yellow phosphor with the Stokes shift and wide-band emission（PC LEDs）,which limits the maximum luminous efficacy with industrialization value.In addition,traditional packaged LEDs cannot be directly used in lighting with high efficiency,perfect lighting effect and low glare because of their Lambertian radiation distribution and super high luminance.The luminous efficacy limit of the solid state lighting is investigated based on the colorimetry theories.Results show that the luminous efficacy limits of the three-color mixing LEDs can be as high as 430 lm/W with Ra〉80 at any white light chromaticities,and they are far higher than those of the PC LEDs.A series of achievements on LED optical system design finished by our group are summarized in this paper.To make the light distributions of the LED sources meet the lighting requirements,the non-imaging optics design theories based on the variable separation method and the feedback iteration method are proposed.For the application of the LEDs in the road lighting,a high energy efficient freeform optical system is obtained with the maximum luminance/illuminance ratio as well as satisfying the lighting requirements provided by Commission Internationale Del′Eclairage（CIE）.For the application of the LEDs in the interior lighting,low glare,softly emitting and modularizing LED surface source is obtained by utilizing micro-ens diffusers designed with the non-imaging optics theories.Uniform collimating multi-surface optical systems are introduced for special lighting application.