Spherical lenses, also known as singlets, are transparent optical components consisting of one or more pieces of optical glass with surfaces curved to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.  

There are seven main spherical lens forms, or shapes, that determine the imaging characteristics of the lens.  They are plano-convex, plano-concave, convex-convex, concave-concave, meniscus, aspheric, and ball.  Plano-convex lenses have a positive focal length, which makes them ideal for collecting and focusing light for many imaging applications.  Plano-concave lenses have a negative focal length and are used for image reduction or to spread light.  Convex-convex lenses have a positive focal length and are useful for 1:1 imaging and in multi-element systems. Also known as biconvex or equiconvex.  Concave-concave lenses have negative focal length, and are used for image reduction and to spread light. Also known as biconcave or equiconcave. Meniscus lenses can increase the numerical aperture of a positive lens assembly, without an undue increase in the aberrations. Aspheric lenses compensate for spherical aberration and are used primarily for their light gathering ability. Ball lenses are used to provide short focal lengths for use with collimated light.  They are often used in fiber coupling applications.  While the above seven are the most common types, there are other, rare styles of spherical lenses available.

Optics and optical components covers all manner of devices that are used to manipulate or control light. These components either use electrical or electronic means to manipulate light, such as occurs with lasers, diodes, photomultipliers and optoelectronic sensors, or they can force the manipulation via material means. This second grouping includes items such as lenses, spherical lenses, filters, beamsplitters, mirrors, diffusers, plates, prisms, and windows. A subgroup of this category is fiber optics. This grouping includes all products that are used to transmit light via transparent glass or plastic fibers. Items within the optics and optical components category fall into four loose families: Light Sources, Optical Components, Optoelectronics, and Fiber Optics. 

Optical components are items that are used to bend, split, diffuse, reflect or otherwise alter or refocus light wavelengths. This may include changing the spectrum of the light, transforming a light pattern into an electric one (image), or simply altering the direction or path. These items generally function without an outside power source, although they may be part of a larger system that does require a power source. Typical components within this family include lenses, spherical lenses, filters, beamsplitters, mirrors, diffusers, plates, prisms, and windows.