HSDL-3003 datasheet(20/21 Pages) HP

20 / 21 page

Shape of the Window

From an optics standpoint, the

window should be flat. This

ensures that the window will not

alter either the radiation pattern

of the LED, or the receive pattern

of the photodiode.

If the window must be curved for

mechanical or industrial design

reasons, place the same curve on

the back side of the window that

has an identical radius as the

front side. While this will not

completely eliminate the lens

effect of the front curved surface,

it will significantly reduce the

effects. The amount of change in

the radiation pattern is dependent

Curved Front and Back

(Second choice)

Curved Front, Flat Back

(Do not use)

Flat Window

(First choice)

upon the material chosen for the

window, the radius of the front

and back curves, and the distance

from the back surface to the

transceiver. Once these items are

known, a lens design can be

made which will eliminate the

effect of the front surface curve.

The following drawings show the

effects of a curved window on the

radiation pattern. In all cases,

the center thickness of the

window is 1.5 mm, the window is

made of polycarbonate plastic,

and the distance from the

transceiver to the back surface of

the window is 3 mm.

HSDL-3003 Datasheet(PDF) 20 Page - Agilent(Hewlett-Packard)