Why Use An Off-Axis Parabolic Mirror To Focus?

We learned from the Ir Aspherical Lens Manufacturer that the ideal optical focusing element transforms a plane wave into a spherical wave, and gathers the energy of each part of the wavefront to the center of the spherical wave at the same time. The size of the focal point is determined by the diffraction limit. . Commonly used focusing elements are single lens, Fresnel lens, double cemented lens, spherical mirror, parabolic mirror and off-axis parabolic mirror (OAP), etc. Focusing on ultra-short and ultra-strong lasers, OAP is used in most cases, which is determined by the geometrical optics and nonlinear optical characteristics of these components.

Spherical lens

First, the lens has spherical aberration. The light near the optical axis is focused to a relatively far place, and the light far away from the optical axis is focused to a relatively close place. In the horizontal direction, all rays of light cannot intersect at one point, but form a fuzzy circle.

Second, the lens has chromatic aberration, the long-wave refractive index is small, and the short-wave refractive index is large, so the long-wave focal length is long and the short-wave focal length is short. The lens cannot focus light of all wavelengths to one point.

Third, the lens material has chromatic dispersion. When the laser passes through the lens, the edge ray passes through a shorter material and the central ray passes through a longer material, so that the pulse wavefront and isophase plane no longer overlap. As a result, the edge ray is earlier than the central ray. To reach the focus, the time difference between the two is.

Aspherical Lens

Doublet lens

The doublet lens corrects the spherical aberration, so the edge and center of the beam can reach the focus at the same time.

Spherical mirror.

The spherical mirror has no chromatic aberration and dispersion (the dispersion of the coating is not considered here), and there is no nonlinear effect of the medium. Like a spherical lens, a spherical lens has a spherical aberration, the far-axis light focuses closer, and the paraxial light focuses farther.

Off-axis parabolic mirror

If the target is placed at the focal point of the parabola, it will block a part of the incident light, so only a part of the parabolic mirror is used to make the beam incident off-axis. This is the off-axis parabola mirror (OAP, Off-Axis Parabola). Using off-axis parabolic mirrors, the incident light will not be blocked by the target.

If you want to buy Ir Aspherical Lens and Aspherical Lens, welcome to contact our infrared spherical lens manufacturer.