According to the characteristics of the light surface of the light-emitting tube, it is divided into round lamp, square lamp, rectangular, surface light-emitting tube, lateral tube, microtube for surface installation, etc. Round lights are divided into φ2mm, φ4.4mm, φ5mm, φ8mm, φ10mm and φ20mm according to the diameter. Foreign countries usually record φ3mm light-emitting diodes as T-1; Write φ5mm as T-1 (3/4); Write φ4.4mm as T-1 (1/4).

The angular distribution of circular luminous intensity can be estimated from the half-value angle size. From the luminous intensity angle distribution map, there are three categories:

(1) High directivity. It is generally a pointed epoxy package or a package with a metal reflector without scattering agent. The half-value angle is 5 ° ~ 20 ° or less, with high directivity, can be used as a local lighting source, or combined with the light detector to form an automatic detection system.

(2) Standard type. Usually used as an indicator light, its half-value angle is 20 ° ~ 45 °.

(3) Scattering type. This is an indicator with a large viewing angle, the half-value angle is 45 ° ~ 90 ° or larger, and the amount of scattering agent is large.