Surgical shadowless lights are used to illuminate the surgical site for optimal viewing of small, low-contrast objects at various depths in incisions and body cavities. Since the operator's head, hands and instruments may cause disturbing shadows to the surgical site, the surgical shadowless lamp should be designed to eliminate shadows as much as possible and minimize color distortion. In addition, the shadowless lamp must be able to work continuously for a long time without emitting excessive heat, which can cause discomfort to the operator and dry the tissue in the surgical field.

Principle:
The operating shadowless light is not actually "shadowless", it just reduces the umbra, making the umbra less obvious. Shadows are formed when light hits an object. Shadows are different everywhere on earth. Carefully observe the shadow under the electric light, and you will find that the shadow is particularly dark in the middle and slightly lighter around. The dark part in the middle of the shadow is called the umbra, and the dark part around it is called the penumbra. The generation of these phenomena is closely related to the linear propagation of light. If a cylindrical tea container is placed on the table and a candle is lit next to it, the tea container will cast a clear shadow. If two candles are lit next to the tea container, two shadows that overlap but do not overlap will be formed. The overlapping part of the two shadows has no light at all, and is completely black, which is the umbra; the place where only a candle can shine next to the umbra is the half-light and half-dark penumbra. If three or even four candles are lit, the umbra will gradually shrink and the penumbra will appear many layers. It is also true that objects can generate shadows composed of umbra and penumbra under electric light. Obviously, the denser the light source of the illuminating object surrounds the illuminated object, the smaller the umbra. If we light a circle of candles around the aforementioned tea container, the umbra disappears completely, and the penumbra fades out of sight. Scientists have made a shadowless lamp for surgery based on the above principles. It arranges the lamps with high luminous intensity into a circle on the lamp panel to synthesize a large-area light source. In this way, light can be irradiated on the operating table from different angles, which not only ensures sufficient brightness of the surgical field of view, but also does not produce obvious umbra, so it is called a shadowless lamp.

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