Lens and light emitting module for surface illumination

A light-emitting module, comprising:

• a circuit board;
• a light-emitting device disposed on the circuit board;
• and
• a lens disposed on the circuit board, the lens configured to distribute light emitted from the light-emitting device,
• wherein the lens comprises:
• a first surface comprising a concave portion having an incidence surface configured to receive light emitted from the light-emitting device, and
• a second surface through which the light incident on the incidence surface of the concave portion exits,
• wherein the second surface comprises a flat portion disposed intersect a central axis, and a convex surface surrounding the flat or concave portion,
• wherein the light-emitting device is disposed within the concave portion of the first surface of the lens,
• wherein the incidence surface of the lens is an inner surface of the concave portion of the first surface of the lens,
• wherein the incidence surface of the lens comprises an upper end surface and a side surface extending from the upper end surface and continuing to a planar surface,
• wherein the first surface of the lens further comprises the planar surface, the planar surface surrounding the concave portion of the first surface of the lens and being entirely within a circumference of the flat portion of the second surface of the lens, and
• wherein the flat portion and the convex surface of the second surface comprise a continuous curve.