Surgical shadowless lamp can be avoided when the operation of the hand and medical equipment to produce a black shadow, to clarify the principle of it!

First introduce the shadowless lamp origin: the shadow is the formation of light irradiation object. Shadows are different everywhere on earth. The Arctic Circle is the shadow of the "big country", because the sunlight there is oblique, the shadow in the vast snowy plains stretch far; equatorial zone is the shadow of the "small people's country", because the sun is high in the sky, the shadow becomes very small.

Look closely at the shadow under the electric light, you will find that the middle of the shadow is particularly dark, surrounded by a little lighter. The part of the shadow that is particularly dark in the center is called the principal shadow, and the surrounding area is slightly lighter. The darker part of the shadow is called the umbra, and the darker part of the shadow is called the penumbra. These phenomena are closely related to the linear propagation of light.

If you put a column-shaped tea canister on the table, next to a candle lit, the tea canister will cast a clear shadow. If two candles are lit next to the tea caddy, two overlapping shadows will be formed without overlapping. The two shadows overlap part of no light at all, is completely black, this is the original shadow; the original shadow next to only one candle can be lighted, is half-light and half-dark penumbra. If three or even four candles are lit, the penumbra part will gradually shrink, and the penumbra part will appear in many layers. This is the same reason why an object under an electric light produces a shadow consisting of a primary shadow and a penumbra. An electric light is emitted by a curved filament and is not confined to a single point. The light coming from one point is blocked by the object, and the light coming from some other points is not necessarily blocked. Obviously, the larger the area of the light-emitting object, the smaller this shadow. If we light a circle of candles around the above tea canisters, then the shadow completely disappears, penumbra is also too faint to see.

Focus: Scientists have made a surgical shadowless lamp based on the above principle. It will be a great intensity of light in the lamp disk arranged in a circle, synthesized into a large area of the light source. In this way, the light from different angles to the operating table, not only to ensure that the surgical field of vision has enough brightness, but also does not produce a clear shadow, so the name shadowless lamp.