Low distortion wide angle lens for dynamic perspective

摘要

An f-theta lens system for a camera that provides a wide field-of-view, relatively low distortion, and a compact footprint. The lens system comprises four molded plastic elements with seven aspheric surfaces. Within a total thickness of 2.5 millimeters, the system is able to provide an image that is 1.2 millimeters across with a horizontal field of view of 127 degrees. The images produced by the system are well-suited for use with conventional face tracking algorithms designed to process rectilinear images produced by cameras with a narrower field of view.

主权项

1. An apparatus comprising:
a four-piece optical lens system, the four-piece optical lens system comprising, in order from an object side to an image side: a first lens element having a first refractive power that is negative, a convex object-side surface, and a concave image-side surface, the first lens element being composed of a first material having a first refractive index and a first Abbe number, the concave image-side surface of the first lens element being aspheric; a second lens element having a second refractive power that is positive, a convex object-side surface, and a concave image-side surface, the second lens element being composed of a second material having a second refractive index and a second Abbe number, both of the convex object-side surface and the concave image-side surface of the second lens element being aspheric; a third lens element having a third refractive power that is positive, a convex object-side surface, and a convex image-side surface, the third lens element being composed of a third material having a third refractive index and a third Abbe number, both of the convex object-side surface and the convex image-side surface of the third lens element being aspheric; and a fourth lens element with a fourth refractive power that is negative, a concave object-side surface, and a convex image-side surface, the fourth lens element being composed of a fourth material having a fourth refractive index and a fourth Abbe number, both of the concave object-side surface and the convex image-side surface of the fourth lens element being aspheric; and an image sensor arranged on the image side of the fourth lens element at an image plane of the four-piece optical lens system, wherein:
the four-piece optical lens system is an F-theta lens system;the four-piece optical lens system provides the image sensor with a field-of-view of at least 120 degrees;a magnitude of the fourth refractive power is less than 10% of a magnitude of the third refractive power;the fourth lens element is a field flattener;fourth order aspheric constants α4 of the concave object-side and the convex image-side surfaces of the fourth lens element are approximately equal;the first refractive index is larger than the third refractive index and is larger than the fourth refractive index;the second refractive index is larger than the third refractive index and is larger than the fourth refractive index;the first Abbe number is smaller than the third Abbe number and is smaller than the fourth Abbe number; andthe second Abbe number is smaller than the third Abbe number and is smaller than the fourth Abbe number.