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What Are Sperical Aberration Compensation Plates?
19/07/01

Optical aberrations are deviations from a perfect, mathematical model. It is important to note that they are not caused by any physical, optical, or mechanical flaws. Rather, they can be caused by the lens shape itself, or placement of optical elements within a system, due to the wave nature of light. Optical aberrations are named and characterized in several different ways. For simplicity, consider aberrations divided into two groups: chromatic aberrations, present when using more than one wavelength of light; and monochromatic aberrations, present with a single wavelength of light.

Spherical aberration
One of the most common types of monochromatic aberrations is spherical aberration. Spherical aberration is the result of light focusing at different locations based on its radial distance from the lens center resulting in poor system performance. Though spherical aberration is present in all spherical optics, an innovative way to correct for it is by employing spherical aberration compensation plates to reduce or remove known quantities of spherical aberration in a system.

By compensating and correcting for a known amount of spherical aberration, spherical aberration compensation plates are single-element optical components that can be easily inserted into a system, reducing spot size and drastically improving image quality. These corrector plates signify a change in the way aberration correction can be handled. By correcting for known amounts of spherical aberration, they save in design time, reduction of system weight as well as manufacturing costs.

Spherical aberration compensation plates are designed to be used in collimated space near a pupil. They should be used for systems that have small fields of view such as laser systems or applications imaging point-like objects. These corrector plates can be combined to induce the desired amount of compensatory spherical aberration. Negative sign plates create over corrected spherical aberration, while positive plates create under corrected spherical aberration.
Spherical aberration compensation plates are optically flat windows with low wavefront distortion that have been magnetorheologically polished to impart a mild aspheric surface.

Spherical aberration compensation plates represent a shift in the paradigm for how optical designers and industrial end-users compensate and overcome spherical aberrations. They generate a new level of flexibility allowing for aberration correction to take place at the design phase, prototyping phase, or post production phase. Additionally, these corrector plates allow users to passively correct for known amounts of aberrations without a complete system redesign and without the inclusion of software and adaptive optics controls, saving time and money.

Historically, options for correcting spherical aberration have been expensive and cumbersome. These options include the use of adaptive optical systems, liquid lenses, or magnetorheological finishing of the final element in an assembly. In each of these cases, the process for reducing the spherical aberrations can be costly and extremely time intensive; making these solutions not well suited for OEM applications. Fortunately, the implementation of a single spherical aberration compensation plate is two orders of magnitude less expensive than most readily available adaptive optical systems.

Depending on their implementation, spherical aberration compensation plates can be used to improve system performance while reducing the total number of optical elements and thus reducing system weight, assembly time, and cost. As a component-level optic, the applications and benefits of these corrector plates are only limited by the creativity of their end-users.

Spherical aberration compensation plates represent the beginning of a new concept for complete aberration correction. As a result, it now seems possible to solve other aberrations by simply implementing a single optical component into the system level design without requiring a complete system redesign. These corrector plates represent a change in how aberration correction is done and pave the way for additional aberration correction plates.