The difference between spherical and aspherical lenses
Due to the high incidence of myopia in recent years, friends with glasses can be seen almost everywhere around us. From the perspective of optical correction, refractive surgery such as excimer laser is undoubtedly an ideal choice, but considering other factors such as economic convenience, glasses are still the first choice for myopic friends. Plane windows, spherical lens manufacturers, reticle gun sight manufacturers, optical lens manufacturers.
When we choose lenses, what we often hear is the spherical lens and aspherical lens mentioned by spherical lens manufacturers and sellers. So what's the difference between the two and how to choose?
What is spherical aberration?
Here we need to clarify an optical concept: spherical aberration, referred to as spherical aberration.
Spherical aberration refers to the fact that the concentric beam emitted by the point on the axis is no longer a concentric beam after passing through the optical system. The light rays of different incident heights of spherical lens manufacturers intersect the optical axis at different positions, and the relative paraxial image point (ideal image point) is different. Degree of deviation, this deviation is spherical aberration.
For the human eye, ideally, the light rays are refracted by the human eye and then converged into a single point. When there is spherical aberration, the beam emitted by the object point on the viewing axis of the spherical lens manufacturers will no longer intersect at one point after being refracted by the human eye. If the far-axis rays converge in front of the focal plane to form positive spherical aberration, and the far-axis rays converge behind the focal plane to form negative spherical aberration.
For spherical lenses, spherical aberration will occur after refraction. Thereby reducing the sharpness and contrast sensitivity of imaging. For general spherical lenses, the positive lens worn by the spherical lens manufacturers for hyperopia will produce negative spherical aberration, and the negative lens worn by myopic eyes will produce positive spherical aberration. The human eye itself generally has a certain positive spherical aberration. If the spherical lens is used for myopia, it will further increase the spherical aberration and reduce the visual quality. Therefore, the advantages of aspherical lenses are beyond doubt.
But everyone's eyes are different, and the spherical aberration and positive and negative states of each person's eyes are also inconsistent. As the age changes, the spherical aberration will drift in the direction of positive spherical aberration accordingly. Therefore, if you want to personalize a pair of glasses that suit you, it is very necessary to conduct a more in-depth spherical aberration check.
