1. Prism definition
A transparent object surrounded by two intersecting planes, used to split light or disperse light beams.
The side of the prism: the plane where light enters and exits is called the side.
The main section of the prism: the plane perpendicular to the side is called the main section.
According to the shape of the main section, it can be divided into three prisms, right-angle prisms, pentagonal prisms and so on. The main cross section of the prism is triangular. The prism has two refracting surfaces, the angle between them is called the apex angle, and the plane facing the apex angle is the bottom surface.
2. Prism structure
The basic structure of a prism mainly includes refractive surface, edge, vertex, and vertex angle.
Refractive surface: The three surfaces of the prism are called refractive surfaces.
Edge: The three straight lines formed by the intersection of three refractive surfaces are called edges.
Top: Choose the edge with the smaller angle formed by the refractive surface in the optics as the top.
3. Prism calculation formula
4. Bottom image marking method of prism
According to the optical properties of prisms, it can be seen that in optometry, prisms are used to correct vision to shift the vision to the top. Therefore, when placing an order, it is not only necessary to record the amount of prism, but also to mark the direction of the prism. The representation of the prism bottom has four basic directions, namely bottom-up (BU), bottom-down (BD), bottom-in (BI), and bottom-out (BO).
The British notation law divides the eyes into four quadrants: “upper inner”, “upper outer”, “lower inner”, and “lower outer”, and mark the direction of the prism base to indicate the position and reading. It should be noted that for the left eye, 0 degrees means bottom-out, and 180 degrees means bottom-in. The opposite is true for the right eye. 0 degrees means bottom inward, and 180 degrees means bottom outward. When using this method, it is necessary to indicate whether it is the right eye or the left eye to avoid ambiguity.
Note: When placing an order, please note the amount of prism and the direction of the prism base.
Post time: Jun-03-2019