Lens device

1. A lens device for directing light beams from a light emitter which has an emitter axis in a front-rear direction, said lens device comprising at least one optical lens which includes

a rear lens segment having

a recess extending forwardly from a rear end of said rear lens segment along the emitter axis to terminate at a first refractive surface, said recess having a second refractive surface which extends in the front-rear direction to interconnect said rear end and said first refractive surface, and which extends circumferentially to surround the emitter axis, and

a reflective surface diverging forwardly from an outer periphery of said rear end to surround the emitter axis and to form an outer peripheral surface of said rear lens segment; and

a front lens segment extending forwardly from said rear lens segment along the emitter axis to terminate at a convex lens front which defines a rear focal region that is located rearwardly of said rear lens segment,

wherein said first refractive surface is configured such that when the light beams from the light emitter enter said optical lens through said first refractive surface to form a plurality of first refracted light beams in said optical lens, a plurality of first imaginary lines, which extend rearwardly and respectively from the first refracted light beams, converge at a first focal region;

wherein said second refractive surface and said reflective surface are configured such that when the light beams from the light emitter enter said optical lens through said second refractive surface and then are reflected by said reflective surface to form a plurality of reflected light beams, a plurality of second imaginary lines, which extend rearwardly and respectively from the reflected light beams, converge at a second focal region overlapping with said rear focal region;

wherein said first focal region overlaps with said rear focal region;

wherein said rear focal region has a rear focal point on the emitter axis;

wherein said second refractive surface has a selected region such that when the light beams from the light emitter enter said optical lens through said selected region of said second refractive surface to form a plurality of second refracted light beams in said optical lens, a plurality of third imaginary lines, which extend rearwardly and respectively from the second refracted light beams, converge at a third focal point;

wherein said third focal point and said rear focal point of said rear focal region cooperatively define a hyperbola which has a distal branch and a proximal branch relative to said third focal point, the proximal branch having a distal arm and a proximal arm relative to said selected region of said second refractive surface; and

wherein said reflective surface is formed by rotating the proximal arm about the emitter axis.

2. The lens device according to claim 1 , wherein said convex lens front is a dome-shaped convex surface such that said rear focal region is in a shape of a point or a ball at said rear focal point.

3. The lens device according to claim 2 , wherein each of said first and second focal regions is in a form of a point, and fully overlaps with said rear focal point.

4. The lens device according to claim 1 , wherein said convex lens front is an arch-shaped convex surface such that said rear focal region is in a shape of a line in a left-right direction, and said line intersects the emitter axis at said rear focal point.

5. The lens device according to claim 4 , wherein each of said first and second focal regions is in a form of a point, and fully overlaps with said rear focal point.