Lens holders are used to stabilize and maintain the position of all of the optical components in a lens assembly. The primary purpose of a lens holder is to provide stability and keep optical elements firmly in place. Lens holders can also be used with filters, polarizers, pinholes, and many geometrically adaptable elements. The proper selection of a lens holder depends upon the application, optical element, required degree of precision, and number of directions along which adjustments will be made. Cost may be an additional consideration, depending upon the number of optical components involved.
There are many types of lens holders that can be used to hold lenses with a variety of shapes and characteristics. Common lens holders include fixed lens holders, fixed lens holders with retaining rings, two-axis lens holders, universal lens holders, and self-centering lens holders. A fixed lens holder with a single screw retainer is a simple, low cost edge-mounting lens holder. A fixed lens holder with a retaining ring is used when moderate precision is required. This is a surface mounted holder, but each holder is specific to a specific lens diameter. A two-axis lens holder is a fixed lens holder with a retaining ring that also allows for vertical and horizontal adjustments of the optical element. Two-axis lens holders provide precise positioning, but each holder is specific to the lens diameter size. A universal lens holder is versatile and can be used with many different lens diameters. Universal lens holders do not cause centration errors and have a fixed position with respect to the optical axis. A self centering lens holder can work with many different lens diameters and the lens center is always aligned with the optical axis. Due to their complexity, these holders can be more expensive than simple lens holders.
Some lens holders may be designed specifically to hold an objectives lens, a series of gauging lenses, or collimators. Other types of lens holders include mirror mounts, prism and cube beamsplitter holders, filter holders, rotary polarizer holders, pinhole and slit holders, fiber optic holders, and cylindrical laser holders.