An opaque lens refers to an object that is typically considered opaque but can be made to act as a lens, specifically for focusing light sharply.
Traditionally, we think of lenses as transparent materials like glass or plastic that refract (bend) light to focus it. However, research has shown that even opaque objects can manipulate light in a similar way.
According to the provided reference, an opaque object acts as a lens that focuses light sharply by exactly matching the wavefront of the incident light to scattering in the opaque object.
This means that instead of relying on simple refraction, the light waves hitting the opaque object are carefully shaped before they enter the object. This pre-shaping is done in such a way that the complex scattering of light within the opaque material results in the light exiting the object and converging to a sharp focus.
Consider the difference:
- Traditional Lens: Light passes through a transparent material, and its shape bends the light rays to converge.
- Opaque Lens: Light wavefronts are specifically tailored before entering the opaque material. The internal scattering, instead of randomly diffusing the light (as seen when a little light that is transmitted forms a speckle pattern for an unshaped wavefront), is used constructively to achieve focus.
In essence, the opacity isn't eliminated, but the way light interacts with the opaque structure is precisely controlled. This control transforms the scattering medium into a functional optical element – an opaque lens capable of sharp focus.
