Difference Between Mirror And Lens

Optical mirror and optical lens are very important optical components in optical systems.

The differences between them are mainly concentrated in:

• Working principle
• Materials and structure
• Focus and imaging
• And application areas

In terms of working principle:

Optical mirror is the reflection of light on the surface and follows the law of reflection. That is, the angle of incidence = angle of reflection. In terms of energy loss, the reflection of the optical mirror may be accompanied by absorption or scattering, which mainly depends on the coating.

The light of the optical lens acts by refraction, that is, the light is deflected when passing through a transparent medium. The physical basis followed by the optical lens is Snell’s law. It is accompanied by partial reflection, absorption and dispersion when it refracts.

In terms of materials and structure

The substrate of the optical mirror is generally glass or metal, and a reflective film layer is coated on the surface or curved surface. Most of the film layers are gold film, silver film, aluminum film, copper film or dielectric film. The main function of the optical mirror is to enhance reflection and reduce absorption.

The base of an optical lens is generally a transparent material, such as glass, plastic or quartz lamp. Its main working mode is to coat an anti-reflection film on at least one curved surface, such as a biconvex, plano-convex or concave-convex lamp surface, and its main function is to reduce the reflection of the surface.

Focus and imaging

The focus type of an optical mirror is a real focus for a concave mirror and a virtual focus for a convex mirror. In terms of imaging, it can form an image or a virtual image, but this mainly depends on the type of mirror.

The focus of an optical lens is opposite to that of an optical mirror. A convex lens has a real focus and a concave lens has a virtual focus. It can also form a real image or a virtual image, which also depends on the type of lens.

Application field

The core function of an optical mirror is to control the direction of the light path, so it is mainly used in scenes that require high reflection, low absorption and no chromatic aberration, such as laser resonant cavity, beam steering, astronomical telescope, telescope, optical interferometer, spectrometer, projector, AR glasses, scanning galvanometer, etc.

The core function of an optical lens is to control the convergence and divergence of light. Therefore, it is mainly used in scenes that require transmission, focusing or dispersion control, such as camera lenses, microscope imaging systems, endoscopes, ophthalmic equipment, fiber coupling, optical communication modules, focused or collimated beams, lidar, vehicle-mounted cameras, and vision correction such as glasses.

In general, if you are processing high-power lasers, have no wavelength dependence, and have light path steering or folding, choose an optical mirror. If you are in scenes such as transmission imaging, focusing/divergence control, and multi-wavelength compatibility, choose an optical lens.