Eyepiece
The present invention provides an eyepiece. The eyepiece is composed of one lens, which comprises a first surface and a second surface that are opposite, wherein, the first surface is a curved surface, and the second surface is a Fresnel structure surface; the Fresnel structure surface is formed by a plurality of annular zones that are sequentially arranged, to form a sawtooth surface, and each of the annular zones is formed by a working surface and a non-working surface, the working surface is an aspheric surface, and the non-working surface is a straight bevel; and the eyepiece satisfies the following conditional expression: 85°<FOV<130°, and 0°≤θi≤5°; wherein, FOV is a maximum angle of view of the eyepiece, and θi is the angle between the non-working surface of the ith annular zone and the optical axis.
1. An eyepiece, composed of one lens, having a first surface and a second surface that are opposite, wherein, the first surface is a curved surface, and the second surface is a Fresnel structure surface; the Fresnel structure surface is a sawtooth surface formed by a plurality of annular zones that are sequentially arranged, and each of the annular zones is formed by a working surface and a non-working surface; and
wherein the eyepiece satisfies 85°<FOV<130°, where FOV is a maximum angle of view of the eyepiece;
wherein, on the second surface, a width zi of the i-th annular zone that is counted from a near optical axis of the second surface towards an edge of the second surface satisfies 0.08 mm≤zi≤3.5 mm; and a depth di of the i-th annular zone satisfies 0 mm<di≤0.5 mm; and
wherein, the first surface is provided thereon with a plurality of periodic phase annular zones, a descending step is provided between any two neighboring periodic phase annular zones located from a near optical axis of the first surface towards an edge of the first surface, each descending step has a depth t equal to that of other descending step, and the depth t of the descending step satisfies 0.0005 mm<t<0.0025 mm, wherein the depth of the descending step is a distance measured parallel to an optical axis of the eyepiece.
2. The eyepiece according to claim 1 , wherein: in the second surface, the working surface of the i-th annular zone is an aspheric surface, and the non-working surface of the i-th annular zone is a straight bevel, wherein an angle θi between the non-working surface of the i-th annular zone and the optical axis satisfies: 0°<θi<5°.
3. The eyepiece according to claim 1 , wherein: the plurality of annular zones in the Fresnel structure surface of the second surface of the eyepiece are arranged on a basal surface, and the basal surface is a flat surface.
4. The eyepiece according to claim 1 , wherein: the plurality of annular zones in the Fresnel structure surface of the second surface of the eyepiece are arranged on a basal surface, and the basal surface is a curved surface.
5. The eyepiece according to claim 1 , wherein, the eyepiece satisfies: 0<SAG1/DY<0.2 where, SAG1 is an axis distance between an intersection point of the first surface and the optical axis and a vertex of an effective radius of the first surface; and DY is an effective external diameter of the eyepiece.
6. The eyepiece according to claim 1 , wherein, the eyepiece satisfies: 7 mm≤ED≤20 mm where, ED is an axis distance between a pupil of a human eye and the first surface when the eyepiece is working.
7. The eyepiece according to claim 1 , wherein, the eyepiece satisfies: 25 mm≤EFL≤50 mm where, EFL is an effective focal length of the eyepiece.
8. The eyepiece according to claim 1 , wherein, the eyepiece satisfies: 0.02<CT/DY<0.4 where, CT is a center thickness of the eyepiece, and DY is an effective external diameter of the eyepiece.