Page 69 - Sensors and Control Systems in Manufacturing

The Role of Sensors in the 21st Century

FIGURE 1.14 A non-phosphor white LED at 19.28 mA. 31

• T1-3/4 (5mm) diameter
• Lens color: water clear
• With flange
• Solder leads without stand-off
Features:
• Emitted color: white
• High luminous intensity
• Technology: InGaN/Sapphire

1.14.1 Non-Phosphor White LEDs
A non-phosphor white LED is a 5-mm round LED made of a clear
epoxy case. This type is unlike most other white LEDs because it does
not use a phosphor but emits white light directly. The operating
chemistry is like ZnSe (zinc selenide)—there is one peak at ~460 nm
and another stronger peak at ~560 nm. This is a normal trend for a
non-phosphor white LED.
The beam consists of a small hotspot surrounded by a larger,
mainly circular corona (Fig. 1.14). Unlike the other ZnSe, a white LED
does not have a yellow color—dark amber to orange—or a brown
perimeter in its beam. The beam of this LED mostly lacks that par-
ticular feature. It provides only a very narrow ring at the perimeter
that may have a yellow tint but that is rather faint.
Two peaks are spaced relatively close to one another, Fig. 1.15.
These LED emissions have no phosphor, Figs. 1.16 to 1.19.