Are brightness and illumination contradictory to LED street lights?

On April 25, 2009, Aladdin Lighting Network invited domestic authoritative experts to hold the "Rational Call Behind the Hot Trend - 2009 LED Application Product Achievement and Trend Seminar" in Shenzhen to share high-level wisdom achievements with LED lighting companies, designers and terminal owners. A lively discussion was held at the seminar.

An audience member asked Mou Tongsheng, the leader of the international OLED standard project, a member of the international standard expert group for LED backlight and light radiation safety, and an associate professor of the Department of Optoelectronics and Optical Information Engineering at Zhejiang University, about the contradiction between the brightness of LED street lamp design and the illumination standard; Qian Keyuan, an associate researcher of the Department of Electronic Physics and Laser Devices at the Shenzhen Graduate School of Tsinghua University; and Qian Keyuan, deputy director of the Semiconductor Lighting Laboratory at the Shenzhen Graduate School of Tsinghua University.

Question: I would like to ask Professor Qian and Professor Mou, we know that there are brightness standards and illumination standards in the design of street lamps, how should we consider this issue in the design? If I achieve uniform illumination, I may see bright spots on the road surface.

Mou Tongsheng: I just talked about the illumination and brightness of street lamps. From the perspective of human vision, it should be based on brightness. However, a new problem is that the light beam is now very large. According to the illumination, when we shine the light below, we will definitely see shadows below, which is not good for drivers. We all know when we drive that when we are far away on a cement road, the light shines over and it looks watery. It is not water, but it looks brighter to us. This is a contradiction. In my personal opinion, brightness is more scientific. Of course, these two are definitely contradictory.

Qian Keyuan: Professor Mou just said a lot. Brightness and illumination are contradictory things in street lights. Street lights are not diffuse. The second one is the next 60 meters. If it is raining, even gods cannot achieve uniform brightness. Rainwater is a mirror, and it is a point for drivers. It is impossible to achieve uniform brightness. A very good cement road, no matter who makes the lights, will be very good. The road in Shenzhen with dozens of street lights is very good. You will feel very uniform at night. However, we know that it is difficult to install some asphalt roads. You think it is very uniform, but it is just zebra strips from a distance. The brightness is too related to the reflection of the road surface. No matter how good the road is, it will not work when it rains. This problem should be considered when designing the road. Don't make the zebra strips so obvious. When talking about the brightness of a rectangle in the speech, it is not a rectangle when it is illuminated. That will cause problems. How to cover the light type, the brightness can be uniform, and of course, it is also a good thing for your illumination to be more uniform. Finally, if we consider how good this road is, we dare not write this thing in the standard, so it is over. The uniformity rate is not 100%, which means it is the best. It may take both into consideration. I think this question is very profound, and it may also be encountered when making street lights.