Apparatus for generating high contrast optical signals, and exemplary applications

Abstract

A display apparatus generates a high visibility optical signal, such as an ICON, the ICON comprising a symbol, shape, or other image-like representation. The ICON becomes visible at an observation point during an illumination ON-state. The ICON may be formed as a portion of display medium, for example as a machined portion of a mirror capable of forming images of a scene by reflection in normal operation. The visibility of the ICON in the illumination OFF-state from an observation point is sufficiently low such that the normal operation of the display medium is maintained. The display apparatus may be used in a blind spot warning system for a vehicle. Visible wavelength LEDs, RGB LEDs and/or diode lasers may be utilized as an illumination source. Ultrashort laser processing or other methods for material modification may be utilized to form microscopic features which distribute incident light, increasing the visibility of the optical signal at an observation point in an ON-state, with very low visibility in the OFF-state and minimal effect on the image in the display medium in the OFF state.

What is claimed is: 
     
         1 . A laser-based method, comprising: irradiating a portion of an optical medium with laser pulses, said irradiating removing at least a depth-wise portion of material from a region of said medium, and forming a predetermined pattern of microscopic features arranged in such a way that a detectable optical signal is visible therefrom with illumination from a first source, said medium capable of receiving illumination from a second source, and wherein said region of said medium is essentially indistinguishable from other parts of the medium without illumination from said first source, wherein said region of said optical medium comprises microscopic features formed in said medium, said microscopic features having a size in the range from about 0.5 μm to about 100 μm, increasing the visibility of said optical signal by said forming step causing said microscopic features to be substantially absent of any melted or oxidized region there along, and wherein said forming step forms said microscopic features with ultrashort laser pulses. 
     
     
         2 . The method of  claim 1 , wherein said optical medium comprises a transparent or translucent substrate with a thin, opaque or semi-opaque film. 
     
     
         3 . The method of  claim 1 , wherein said optical medium comprises a mirror, said mirror comprising a transparent substrate and a reflective coating disposed thereon. 
     
     
         4 . The method of  claim 1 , wherein said optical medium comprises a mirror, said mirror comprising a transparent substrate and a reflective coating disposed thereon, and said region comprises microscopic features that substantially diffract energy received from said controllable first source to generate the detectable signal, and said microscopic features are sufficiently small to be nearly invisible without illumination from the first source. 
     
     
         5 . The method of  claim 1 , wherein said microscopic features are formed by selectively removing a depth-wise portion of said reflective coating. 
     
     
         6 . The method of  claim 1 , wherein said ultrashort pulses comprise a pulse width in the range from about 100 fs to about 10 ps. 
     
     
         7 . The method of  claim 1 , wherein said ultrashort laser pulses are generated at a repetition rate of at least about 1 kHz. 
     
     
         8 . The method of  claim 1 , wherein said ultrashort laser pulses are generated at a repetition rate of at least about 100 kHz. 
     
     
         9 . A method comprising: modifying a portion of an optical medium to selectively remove at least a depth-wise portion of material from a region of said medium, and forming a predetermined pattern of microscopic features arranged so that a detectable optical signal is visible therefrom with illumination from a first source, said medium capable of receiving incident illumination from a second source, and wherein said region of said medium is essentially indistinguishable from other parts of the medium without illumination from said first source, wherein said forming step produces features having a size in the range from about 0.5 μm to about 100 μm, and improving visibility of the optical signal by employing ultrashort laser pulses during said forming step so that said features are substantially absent of any associated melted or oxidized region. 
     
     
         10 . The method of  claim 9 , wherein said method further comprises mechanically scribing or etching. 
     
     
         11 . The method of  claim 1 , wherein said method is utilized to make at least a portion of an optical signaling apparatus, a warning indicator for a vehicle, or a visual warning system. 
     
     
         12 . The method of  claim 1 , wherein said microscopic features comprise dots, lines, arcs, or circles. 
     
     
         13 . The method of  claim 1 , wherein said optical signal is in the form of an ICON. 
     
     
         14 . The method of  claim 1 , wherein said melted or oxidized region is a heat-affected zone along said microscopic features. 
     
     
         15 . The method of  claim 1 , wherein said optical medium comprises a translucent or transparent substrate with a thin, opaque or semi-opaque film. 
     
     
         16 . The method of  claim 9 , wherein said method is utilized to make at least a portion of an optical signaling apparatus, a warning indicator for a vehicle, or a visual warning system. 
     
     
         17 . The method of  claim 9 , wherein said microscopic features comprise dots, lines, arcs, or circles. 
     
     
         18 . The method of  claim 9 , wherein said optical signal is in the form of an ICON. 
     
     
         19 . The method of  claim 9 , wherein said melted or oxidized region is a heat-affected zone along said microscopic features. 
     
     
         20 . The method of  claim 9 , wherein said optical medium comprises a translucent or transparent substrate with a thin, opaque or semi-opaque film. 
     
     
         21 . The method of  claim 9 , wherein said optical medium comprises a mirror, said mirror comprising a transparent substrate and a reflective coating disposed thereon. 
     
     
         22 . The method of  claim 9 , wherein said optical medium comprises a mirror, said mirror comprising a transparent substrate and a reflective coating disposed thereon, and said region comprises microscopic features that substantially diffract energy received from said controllable first source to generate the detectable signal, and said microscopic features are sufficiently small to be nearly invisible without illumination from the first source. 
     
     
         23 . The method of  claim 9 , wherein said microscopic features are formed by selectively removing a depth-wise portion of said reflective coating. 
     
     
         24 . The method of  claim 9 , wherein said ultrashort pulses comprise a pulse width in the range from about 100 fs to about 10 ps. 
     
     
         25 . The method of  claim 9 , wherein said laser pulses are generated at a repetition rate of at least about 1 KHz.