Imaging optical system

A terminal comprising:

• an imaging optical system, from an object side to an image side along an optical axis, comprising:
• a first lens group having a convex surface on a most object side;
• a prism comprising:
• a light input surface at which light that has passed through the first lens group is incident;
• a plurality of reflective surfaces that reflect incident light;
• and
• a light output surface from which the light reflected from a last reflective surface of the plurality of reflective surfaces is emitted,
• wherein the plurality of reflective surfaces are arranged so that a chief ray incident from the light input surface is reflected multiple times within the prism so as to self-intersect a chief ray path at least once within the prism;
• a second lens group comprising at least one optical element having negative refractive power;
• an image sensor on which the light that has passed through the second lens group focuses images,
• wherein following condition is satisfied:
• 1
• <
• F
• ⁢
• 1
• /
• F
• ⁢
• 2
• ≦
• 1
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• where F1 is a maximum light flux diameter at an optical surface of the most object side of the first lens group, wherein a light ray focuses images at a center of the image sensor, and F2 is a maximum light flux diameter at an optical surface of the most object side in the second lens group, wherein the light ray focuses images at a center of the image sensor;
• and
• a Graphic Processing Unit (GPU), wherein the GPU is connected to the imaging optical system and receives and processes image signals.