Coating for forming a high definition aperture

Abstract

An optical thin film stack for a dark aperture is deposited using thermal ion-assisted deposition (“IAD”). The IAD provides an energetic deposition of chromium and chromium oxide that results in a dark mirror optical thin film stack with superior etch properties. Edge definition is improved, and the edge profile is controllable by the selection of IAD parameters. An in situ IAD cleaning process can be used to clean the substrate sufficiently so that an intermediate adhesion layer of chromium is not required.

1 . An optical aperture comprising: 
 a substrate,    a dark mirror thin film structure including a plurality of thin film layers; and    a clear field portion of the optical aperture being defined by an aperture edge of the dark mirror thin film structure having a selected edge profile, wherein a density of at least one of the plurality of thin film layers is selected to provide the selected edge profile.    
     
     
         2 . The optical aperture of  claim 1  wherein the dark mirror thin film structure includes a metal layer comprising a metal and an oxide layer comprising an oxide of the metal.  
     
     
         3 . The optical aperture of  claim 1  wherein the selected edge profile is between 30 degrees and 60 degrees.  
     
     
         4 . The optical aperture of  claim 1  wherein the substrate is a glass substrate and the dark mirror thin film structure includes an oxide layer proximate to the glass substrate.  
     
     
         5 . The optical aperture of  claim 1  wherein the dark mirror thin film structure includes a chromium layer having a reflectivity greater than 50%.  
     
     
         6 . The optical aperture of  claim 1  wherein the dark mirror thin film structure includes a chromium oxide layer having a chromium oxide density selected according to the selected edge profile.  
     
     
         7 . The optical aperture of  claim 1  wherein the dark mirror thin film structure includes a chromium metal layer having a chromium metal density selected according to the selected edge profile.  
     
     
         8 . The optical aperture of  claim 1  wherein the dark mirror thin film structure includes at least one chromium oxide layer having a selected chromium oxide density and at least one chromium metal layer having a selected chromium metal density.  
     
     
         9 . The optical aperture of  claim 1  bonded to an optical device package.  
     
     
         10 . An optical aperture comprising: 
 a glass substrate,    a dark mirror thin film structure forming a dark field portion of the optical aperture, the dark mirror thin film structure including a chromium oxide layer disposed on the glass substrate;    a clear field portion of the optical aperture being defined by an aperture edge of the dark mirror thin film structure having a selected edge profile between 30 degrees and 60 degrees.    
     
     
         11 . A dark mirror comprising: 
 a glass substrate;    a first Cr 2 O 3  layer disposed on the glass substrate;    a first chromium layer disposed on the first Cr 2 O 3  layer;    a second Cr 2 O 3  layer disposed on the first chromium layer; and    a second layer of chromium disposed on the Cr 2 O 3  layer, wherein at least one of the first Cr 2 O 3  layer, the first chromium layer, the second Cr 2 O 3  layer, and the second chromium layer has a selected density.    
     
     
         12 . The dark reflector of  claim 11  wherein the second layer of chromium has a reflectivity greater than 50%.  
     
     
         13 - 29 . (canceled).  
     
     
         30 . The optical aperture of  claim 1  wherein the density is selected so as to avoid a bright perimeter of the optical aperture.  
     
     
         31 . The optical aperture of  claim 1  wherein the aperture has an edge definition not greater than 20 microns.