Abstract: A light emitting diode includes a source layer, a metallic plasma generating layer, a first optical symmetric layer, a first electrode, and a second electrode. The source layer includes a first semiconductor layer, an active layer, and a second semiconductor layer stacked in series. The first semiconductor layer includes a first surface and a second surface opposite to the first surface. The first electrode covers and contacts the first surface. The second electrode is electrically connected with the second semiconductor layer. The metallic plasma generating layer is disposed on a surface of the source layer away from the first semiconductor layer. The first optical symmetric layer is disposed on a surface of the metallic plasma generating layer away from the first semiconductor layer. A refractive index difference between the source layer and the first optical symmetric layer is less than or equal to 0.3.

Abstract: A method and device for acquiring latent fingerprint orientation. The method includes: extracting a valid area in a latent fingerprint image; acquiring an orientation field of the valid area and a confidence of coordinate points in the valid area; dividing the orientation field into a first area with a high confidence and a second area with a low confidence; collecting control points in the first area, performing triangulation on control points in the first area and determining differences between control points to determine a set of control points; manually marking control points in the second area, adding control points marked to the set, performing triangulation on control points in the set and determining whether a new manually marked control point is to be added in the set according to a difference determination; and establishing a model for control points in the set to obtain an orientation field of the image.