DVD Recorder User Manual

Shape of the Window

From an optics standpoint, the window should be at.

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 in-

dustrial 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 eect of the front curved surface, it will sig-

nicantly reduce the eects. The amount of change in

the radiation pattern is dependent 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 eect of the front

surface curve.

The following drawings show the eects 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.

Figure 22. Shape of windows.

Curved Front and Back

(Second Choice)

Flat Window

(First Choice)

Curved Front, Flat Back

(Do Not Use)

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