Lens

A lens adapted to image a first image plane at a reduced side onto a magnified side, the lens having an optical axis, and the lens comprising:

• a lens group disposed in a light path between the reduced side and the magnified side;
• and
• a concave reflective mirror disposed in the light path between the lens group and the magnified side;
• wherein an offset of the first image plane with respect to the optical axis is greater than 100%, the offset is defined as
• Offset
• ≡
• Lh
• +
• Ld
• Lh
• ×
• 100
• ⁢
• ⁢
• %
• ,
• where Lh is a width of the first image plane and Ld is a distance between a side of the first image plane closer to the optical axis and the optical axis;
• a throw ratio of the lens is less than 0.3;
• the first image plane has an image point A, an image point B, an image point C, an image point D, an image point E, an image point F, an image point G, an image point H, and an image point I;
• the first image plane has a first side, a second side opposite to the first side, a third side connected with the first side and the second side, and a fourth side opposite to the third side, wherein the fourth side is connected with the first side and the second side;
• the image point A is disposed on an apex connecting the first side and the third side;
• the image point C is disposed on an apex connecting the first side and the fourth side;
• the image point G is disposed on an apex connecting the third side and the second side;
• the image point I is disposed on an apex connecting the fourth side and the second side;
• the image point B is disposed on a midpoint between the image point A and the image point C;
• the image point D is disposed on a midpoint between the image point A and the image point G;
• the image point F is disposed on a midpoint between the image point C and the image point I;
• the image point H is disposed on a midpoint between the image point G and the image point I;
• the image point E is disposed on a midpoint between the image point B and the image point H;
• the image point E is disposed on a midpoint between the image point D and the image point F;
• a reference plane is disposed on a midpoint of a distance between the lens group and the concave reflective mirror, wherein the reference plane is perpendicular to the optical axis;
• a center ray between a plurality of marginal rays emitted from each of the image points A, B, C, D, E, F, G, H, and I is adapted to intersect the reference plane;
• the center rays respectively emitted from each of the image points A, B, C, D, E, F, G, H, and I respectively intersect the reference plane at a reference point a, a reference point b, a reference point c, a reference point d, a reference point e, a reference point f, a reference point g, a reference point h, and a reference point i;
• the lens is disposed in a space defined by a coordinate system constructed by a x-axis, a y-axis, and a z-axis;
• the optical axis and the z-axis overlap each other;
• the x-axis is parallel to the third side and the fourth side;
• the y-axis is parallel to the first side and the second side;
• the x, y, and z axes are perpendicular to each other;
• distances respectively kept by the reference points g, d, a, h, e, and b from an y-z plane are respectively D1, D2, D3, D4, D5, and D6, wherein 1<D4/D1<1.5, 1<D5/D2<1.5, and 1<D6/D3<1.5.