Patent ID: 8749902

Claim:
A lens module, comprising: a barrel; a first lens; a first spacer ring; a second lens having an effective diameter A; a second spacer ring having an inner diameter B; and a third lens having an effective diameter C; wherein, the first lens, the first spacer ring, the second lens, the second spacer ring, and the third lens are coaxially assembled within the barrel, along an axial direction of the barrel in that order; the first spacer ring is sandwiched between the first lens and the second lens, the second spacer ring is sandwiched and located between the second lens and the third lens; the inner diameter B of the second spacer ring is smaller than the effective diameter C of the third lens and greater than the effective diameter A of the second lens; wherein the effective diameter C of the third lens, the inner diameter B of the second spacer ring, and the effective diameter A of the second lens meet the relationships presented in the following equations: 0.098 ≤ C - B C ≤ 0.128 ⁢ ⁢ and ⁢ ⁢ 0.259 ≤ B - A A ≤ 0.301 .