Optical Department

Abstract

The optical system disclosed in the examples includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged sequentially along an optical axis from the object side to the image side, wherein the first lens has a convex object side surface, the second lens has positive refractive power and a convex object side surface, the third lens has negative refractive power and a concave image side surface, the eighth lens has positive refractive power, and at least one of the object side surface and the image side surface has at least one inflection point, and the ninth lens has negative refractive power, and the object side surface and the image side surface have at least one inflection point.

Claims

[Claim 1] It consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens, which are sequentially arranged along the optical axis from the object side to the image side. The first lens has a negative refractive power, and the side surface of the object is convex. The second lens has a positive refractive power and the side surface of the object is convex. The third lens has a positive refractive power and the side surface of the object is convex. The fourth lens has negative refractive power and a concave image surface. The fifth lens has a positive refractive power, The fifth lens has a concave side for the object and a convex side for the image. The sixth lens has a negative refractive power, The seventh lens has a negative refractive power, The eighth lens has a positive refractive power, and at least one of the object side and the image side has at least one inflection point. The ninth lens has a negative refractive power, and the object side and the image side have at least one inflection point. An optical system in which the central thickness of the third lens is greater than the central thickness of the first and second lenses. [Claim 2] The optical system according to claim 1, wherein the central thickness of the third lens is greater than the central thickness of each of the fourth to sixth lenses. [Claim 3] The optical system according to claim 1 or 2, wherein the refractive indices of the fourth, sixth, and eighth lenses are greater than the refractive indices of the first, second, fifth, seventh, and ninth lenses, and are 1.6 or greater. [Claim 4] The optical system according to any one of claims 1 to 3, wherein the Abbe numbers of the first, second, fifth, seventh, and ninth lenses are 50 or more, and the Abbe numbers of the fourth and sixth lenses are less than 30. [Claim 5] The optical system according to any one of claims 1 to 4, wherein the ninth lens has a convex side surface for an object, and the sixth lens has a concave side surface for an object and a convex side surface for an image. [Claim 6] The image side of the ninth lens includes an image sensor and an optical filter between the image sensor and the ninth lens. The optical system satisfies equations 1 and 2, [Mathematics 1] 0<BFL / TTL<0.3 [Math 2] 0<BFL / Img<0.3 The optical system according to any one of claims 1 to 5, wherein BFL is the distance from the vertex of the image side surface of the ninth lens to the image sensor, TTL is the distance from the vertex of the object side surface of the first lens to the image sensor, and Img is the distance from the optical axis to the end of the diagonal in the image sensor. [Claim 7] The image side of the ninth lens includes an image sensor and an optical filter is included between the image sensor and the ninth lens. The optical system satisfies equations 3, 4, and 5. [Mathematics 3] 0.5<F / TTL<1.2 [Math 4] 5<TTL / (Img×2)<0.8 [Math 5] 5<TTL / (D92×2)<1.2 The optical system according to any one of claims 1 to 6, wherein TTL is the distance from the vertex of the object side surface of the first lens to the image sensor, F is the total effective focal length of the optical system, Img is the distance from the optical axis to the end of the diagonal in the image sensor, and D92 is the distance from the vertex of the image side surface of the ninth lens to the end of the effective region. [Claim 8] The third lens has a convex image surface, The optical system according to any one of claims 1 to 7, wherein the radius of curvature of the object side surface of the third lens is L3R1, and when the absolute value of the radius of curvature of the image side surface of the third lens is defined as |L3R2|, the condition 0 < L3R1 / |L3R2| < 0.5 is satisfied. [Claim 9] The third lens has a convex side surface, The optical system according to any one of claims 1 to 8, wherein when the absolute value of the radius of curvature of the object side surface of the fourth lens is |L4R1| and the radius of curvature of the image side surface of the fourth lens is L4R2, the relationship 0.2 < L4R2 / |L4R1| < 1 is satisfied. [Claim 10] The optical system according to any one of claims 1 to 9, wherein when the refractive index of the third lens at 587 nm is G3 and the refractive index of the fourth lens at 587 nm is G4, the relationship 0.7 < G3 / G4 < 1.2 is satisfied. [Claim 11] The optical system according to any one of claims 1 to 10, wherein the central thickness of the first lens is T1, the central thickness of the second lens is T2, and the central thickness of the third lens is T3, satisfying the relationships 0.2 < T2 / T3 < 1 and 0.2 < T1 / T3 < 1. [Claim 12] The seventh lens has a concave surface on the object side and a concave surface on the image side, The eighth lens has a convex side for the object and a concave side for the image. The edge of the object side of the eighth lens protrudes toward the first lens more than the vertex on the optical axis of the object side of the eighth lens, The optical system according to any one of claims 1 to 10, wherein the straight line connecting the edges of the object side surface of the eighth lens is the same as the straight line perpendicular to the optical axis midway between the object side surface and the image side surface of the seventh lens, or is located closer to the first lens. [Claim 13] The optical system according to claim 12, wherein the straight line connecting the edges of the object side surface of the eighth lens is located closer to the first lens than the straight line perpendicular to the optical axis at the vertex of the object side surface of the seventh lens. [Claim 14] The first distance between the fourth lens and the fifth lens along the optical axis is greater than the distance between the second lens and the third lens. The optical system according to any one of claims 11 to 13, wherein the second interval between the eighth lens and the ninth lens along the optical axis is smaller than the first interval. [Claim 15] The optical system according to claim 14, wherein the first and second intervals are 0.7 mm or more. [Claim 16] The optical system according to any one of claims 1 to 15, wherein the central thickness of the third lens is in the range of 2 to 4 times the central thickness of the fourth lens.

Images