What is the principle of shadowless lamp?

In fact, a shadowless lamp can't be a shadowless lamp. It just brightens the umbra and makes it inconspicuous.

Shadows are formed when light shines on objects. Shadows are different in every part of the earth. If you carefully observe the shadow under the electric light, you will also find that the middle part of the shadow is particularly dark and the periphery is slightly shallow. The particularly dark part in the middle of the shadow is called umbra, and the dark part around it is called penumbra. These phenomena are closely related to the linear propagation of light.

If you put a cylindrical tea cone on the table and light a candle next to it, it will cast a clear shadow. If two candles are lit next to the tea cone, two overlapping shadows will be formed. The overlapping part of the two shadows is completely black without light, which is the umbra; Next to the umbra, where only candles can shine, is the penumbra that is half bright and half dark. If three or even four candles are lit, the umbra will gradually shrink and many layers will appear in the penumbra. The same is true for objects that can produce shadows composed of umbra and penumbra under electric lights. Obviously, the larger the area of the luminous object, the smaller the umbra. If we light a circle of candles around the tea cone, the umbra will disappear completely, and the penumbra will be too bright to see.

According to the above principle, scientists have made a shadowless lamp for surgery. It arranges lamps with high luminous intensity in a circle on the lamp board to synthesize a large-area light source. In this way, the light can shine on the operating table from different angles, which not only ensures the sufficient brightness of the surgical field of vision, but also does not produce obvious shadows, so it is called shadowless lamp.