The surface curvature of the aspheric lens is different from that of the ordinary spherical lens. In order to pursue the thinness of the lens, the curved surface of the lens needs to be changed. In the past, the spherical design was used to increase aberrations and distortion, resulting in obvious image blur, distortion of the field of view, and field of view Undesirable phenomena such as narrow and small. The current aspheric design corrects the image and solves the problem of distortion of the horizon. At the same time, it makes the lens lighter, thinner, and flatter. Moreover, it still maintains excellent impact resistance, allowing the wearer to use it safely.
What is an aspheric lens?
In 1638, Johannn Kepler experimented with an aspheric surface on the lens to obtain aspherical aberration image surface at near and far distances, thus gradually laying the foundation for aspheric optics. An aspheric mirror refers to an optical component whose surface is determined by a number of higher-order equations, and the radius of each point on the surface is different. When the light is incident on the aspherical mirror, the light can be focused on one point, and various aberrations can be eliminated, thereby obtaining a high-quality optical image. The specific polynomial higher-order equations are given by:
This formula expresses the surface as the deviation from a cone, Z is the sag of the surface, Y is the height of the light, C is the curvature of the surface on the optical axis, and A4, A6, A8… are the fourth, sixth, 8…sub-aspheric coefficient, k is the conic constant, the relationship between the shape of the aspheric surface and k is as follows:
| K Cone constant | Aspherical shape |
| k=0 | Spherical |
| k=-1 | Paraboloid |
| k<-1 | Hyperboloid |
| -1<k<0 | Ellipsoid, the focus is on the optical axis |
| k>0 | Ellipsoid, the focus is on a straight line perpendicular to the optical axis |
The difference between aspheric mirror and spherical mirror:
There are various aberrations in the spherical lens, which cannot be eliminated by a single spherical lens. However, a single aspheric lens can correct various aberrations such as spherical aberration, coma, astigmatism, and curvature of field, reduce light energy loss, and obtain high-quality image effects and high-quality optical characteristics. Below we analyze the difference in focusing performance between a single spherical lens and an aspheric lens. The same design wavelength is 532nm, the focal length is 50mm, and the output spot contrast is as follows:
In addition, starting from the system design, compared with the spherical system, the aspheric mirror has a simpler structure, a larger field of view, and a clearer image quality. Let’s take a look at the design examples of Cooke’s three-separation objective lens to take a look at the superiority of the aspheric lens. As can be seen in the figure below, in the optically simulated Jingliang Optoelectronic Incubation Park under the design environment with a field of view of 30°, we only replace the fifth surface of the three lenses with an aspheric surface, and the edge distortion can be reduced. The image quality is clearer, closer to a more realistic picture.
