Variable focal distance lens system and imaging device

An imaging device, comprising:

• a variable focal distance lens system configured to form an optical image;
• and
• an imaging element configured to convert the optical image into an electrical signal, wherein the variable focal distance lens system includes:
• a first lens unit that comprises at least one lens group of a first plurality of lens groups;
• a second lens unit that comprises a first freeform-curved surface lens and a second freeform-curved surface lens;
• and
• a third lens unit that comprises at least one lens group of a second plurality of lens groups, wherein
• the first lens unit, the second lens unit, and the third lens unit are in this order from an object side to an image side,
• each of the first lens unit and the third lens unit further comprises a lens that is rotationally symmetrical to an optical axis,
• the lens is on the optical axis,
• a shape of the first freeform-curved surface lens is same as a shape of the second freeform-curved surface lens,
• the first freeform-curved surface lens and the second freeform-curved surface lens are rotated, about the optical axis, at 180 degrees,
• the first freeform-curved surface lens and the second freeform-curved surface lens are movable in a Y-axis direction when optical axes of the first lens unit and the third lens unit are set to be a Z-axis,
• a Y-axis is perpendicular to the Z-axis on an image surface,
• an X-axis is perpendicular to each of the Y-axis and the Z-axis on the image surface,
• a direction of a movement of the first freeform-curved surface lens in the Y-axis direction is opposite to a direction of a movement of the second freeform-curved surface lens in the Y-axis direction,
• a refractive power of the second lens unit varies based on the direction of the movement of the first freeform-curved surface lens being opposite to the direction of the movement of the second freeform-curved surface lens,
• the movement of the first freeform-curved surface lens in the Y-axis direction, the movement of the second freeform-curved surface lens in the Y-axis direction, and a movement of one of the at least one lens group from the first plurality of lens groups or the at least one lens group of the second plurality of lens groups are based on a change of a positional state of each lens of the first lens unit, the second lens unit, and the third lens unit from a wide-angle end state to a telephoto end state,
• a focal distance of the variable focal distance lens system in the wide-angle end state is shorter than a focal distance of the variable focal distance lens system in the telephoto end state,
• the following Conditional Expression (1) is satisfied
• 0.03<ΔP2/Z<0.35 (1),
• Here,
• ΔP2:
• φ2T/φ2W,
• φ2T:
• a first refractive power of the second lens unit in the telephoto end state,
• φ2W:
• a second refractive power of the second lens unit in the wide-angle end state,
• Z:
• ft/fw,
• ft:
• the focal distance of the variable focal distance lens system in the telephoto end state,
• fw:
• the focal distance of the variable focal distance lens system in the wide-angle end state, and
• the refractive power of the second lens unit includes at least one of the first refractive power or the second refractive power.