With focusing and imaging on the working surface and simple rod contour, it is widely used in many micro-optics fields. Its main functions are focusing, collimating and imaging.
Focusing and Collimating
Focusing
According to the transmission principle of Grin Lens, when parallel rays pass Grin Lens from one facet which pitch is 1/4P, the rays will focus on the other facet. The conventional lens can not achieve this kind of facet focal function. (Figure 5)
Collimating
Collimating is the opposite application comparing to focusing. According to the transmission principle of Grin Lens, when convergent rays input from one facet of Grin Lens for 1/4P, the rays will be parallel after passing through the other facet. (Figure 6)
Typical Application
Grin Lens is a basically part in passive component of optical communication. It is used respectively to collimate and focus the rays with output or entry into the fiber. In this way we can add many optical components between two Grin Lenses to form another component of different function, such as collimator, coupler, WDM, optical switch, isolator, etc. (Figure 7)
Coupling and Focus
Grin lens can focus the light by flat surface, also due to its simple rod contour, it is widely used in the course of optical energy transmission and transform. This focus can be applied in many optical coupling fields, for example, fiber and light source, fiber and photoelectric detector, fiber and fiber.
In Figure 8, L1 is the distance from light source to the facet of Grin Lens. L2 is the distance from the facet of Grin Lens to the fiber. Z is the length of Grin Lens. In order to make the light that emit out from light source or fiber be coupled effectively and enter into the fiber by passing through the Grin Lens, we should adjust L1 and L2 so as to improve the coupling efficiency. But in the real coupling process, the coupling efficiency is less than the theory value due to the structure element tolerance and other affection factors.
Imaging
Single Lens Imaging
Beside the conventional lens imaging capability, Grin Lens also has the characteristic of facet imaging.
According to this principle, if we make use of the lens which length is the whole number multiple of 1/2P, Grin Lens can achieve the transmission of imaging from one facet to another facet. More and more Grin Lens of low chromatic aberration is popularly used in all kinds of medical endoscopes and industries endoscopes.
Imaging of Grin Lens Array
When we apply Grin Lens Array to transmit a big picture, the conjugated length can be greatly reduced. On the other hand, the Grin Lens Array what is put in straight line has the same image distinguishing rate, and the transmission function of the whole array is fairly well-distributed, which can enhance the quality of image.
By using Grin Lens Array, the conjugated length will be shorter so as to reduce the overall size of the system. Therefore Grin Lens Array becomes the important device of duplicator, electrograph, scanner, etc.