Optical element and light emitting device

1. An optical element comprising:

a bottom surface;

a total reflection surface located above the bottom surface, wherein the optical element ha a central axis perpendicular to the bottom surface, and the total reflection surface extends outward from the central axis and has a peripheral boundary away from the central axis;

a recess recessed from the bottom surface toward the total reflection surface, wherein the recess has a continuously curved top surface and a continuously curved sidewall, the continuously curved top surface extends from a topmost portion thereof to an edge thereof, the continuously curved sidewall extends from the edge of the continuously curved top surface to a first edge of the bottom surface, and the recess is free of linear portions;

a first light exit surface abutting the peripheral boundary of the total reflection surface and extending toward the bottom surface away from the central axis; and

a second light exit surface abutting the first light exit surface, extending away from the central axis and abutting the bottom surface,

wherein each of the first light exit surface and the second light exit surface consists of at least one linear sub-refractive surface that is not perpendicular to the central axis or not parallel to the bottom surface, and each linear sub-refractive surface is a straight line in any cross section passing through the central axis,

wherein the at least one linear sub-refractive surface of the second light exit surface, comprises a first linear sub-refractive surface and a second linear sub-refractive surface, each of the first linear sub-refractive surface and the second linear sub-refractive surface of the second light exit surface is not perpendicular to the central axis or not parallel to the bottom surface, each of the first linear sub-refractive surface and the second linear sub-refractive surface of the second light exit surface is straight in any cross section passing through the central axis, the second linear sub-refractive surface of the second light exit surface extends directly upwards from a second edge of the bottom surface, and at least a portion of the first linear sub-refractive surface of the second light exit surface extends directly upwards from a top edge of at least a portion of the second linear sub-refractive surface of the second light exit surface.

2. The optical element of claim 1 , wherein the bottom surface has an arithmetic mean deviation greater than 0 μm.

3. The optical element of claim 1 , wherein each of the linear sub-refractive surfaces has an arithmetic mean deviation greater than 0 μm, and the arithmetic mean deviations are the same as or different from each other.

4. The optical element of claim 1 , wherein the at least one linear sub-refractive surface of the second light exit surface comprises a plurality of third linear sub-refractive surfaces, and the third linear sub-refractive surfaces are connected to each other in sequence from top to bottom.

5. The optical element of claim 1 , wherein the at least one linear sub-refractive surface of the first light exit surface comprises a plurality of third linear sub-refractive surfaces, the third linear sub-refractive surfaces are connected to each other in order from top to bottom to connect the total reflection surface and the second light exit surface, and each of the third linear sub-refractive surfaces extends away from the central axis.

6. The optical element of claim 1 , wherein the total reflection surface has a plurality of convex structures, and the convex structures are used to destroy a total reflection mechanism of the total reflection surface.

7. The optical element of claim 1 , wherein at least one of the linear sub-refractive surfaces is an annular curved surface that is rotationally symmetrical with respect to the central axis.

8. The optical element of claim 1 , wherein the total reflection surface is concave toward the bottom surface.

9. A light emitting device comprising:

a driving substrate;

a light emitting element disposed on the driving substrate; and

the optical element of claim 1 disposed on the driving substrate, wherein the recess is used for accommodating the light emitting element.

10. The optical element of claim 3 , wherein the arithmetic mean deviations of the linear sub-refractive surfaces are in a range of 0.5 μm to 40 μm.

11. The optical element of claim 4 , wherein each third linear sub-refractive surface is an annular curved surface that is rotationally symmetrical with respect to the central axis, each annular curved surface has a top boundary and an opposite bottom boundary, and a length of the top boundary is less than or equal to a length of the bottom boundary.

12. The optical element of claim 4 , wherein each third linear sub-refractive surface is an annular curved surface that is rotationally symmetrical with respect to the central axis, each annular curved surface has a top boundary and an opposite bottom boundary, and a first distance between the top boundary and the central axis is less than or equal to a second distance between the bottom boundary and the central axis.

13. The optical element of claim 4 , wherein each third linear sub-refractive surface has an included angle with respect to the bottom surface, and the included angles are less than or equal to 90 degrees.

14. The light emitting device of claim 9 , wherein the light emitting element comprises a light emitting diode.

15. The optical element of claim 13 , wherein the included angles of the third linear sub-refractive surfaces gradually increase from top to bottom.