Compact panoramic camera: optical system, apparatus, image forming method

Abstract

An optical system for a camera includes a convex reflector, a decompression lens, and an image sensor. The convex reflector has a first diameter and a non-parabolic, axially symmetric, aspheric surface that provides a virtual curved and compressed image of a scene having a non-parabolic image compression. The decompression lens is positioned to receive the virtual curved and compressed image. The decompression lens is configured to decompress the virtual curved and compressed image into a real image having a parabolic image decompression and project the real image. The image sensor is positioned to receive the real image. The real image has a second diameter at the image sensor that is less than the first diameter. A ratio of the first diameter to the second diameter is between 6.5:1 and 2.3:1. The optical system provides a polychromatic modulation transfer function of 30% or more for 150 cy/mm.

1 . An optical system for a camera, the optical system comprising:
 a convex reflector having (i) a first diameter and (ii) a non-parabolic, axially symmetric, aspheric surface that provides a virtual curved and compressed image of a scene having a non-parabolic image compression;   a decompression lens positioned to receive the virtual curved and compressed image, the decompression lens configured to:
 decompress the virtual curved and compressed image into a real image having a parabolic image decompression; and 
 project the real image having the parabolic image decompression; and 
   an image sensor positioned to receive the real image having the parabolic image decompression from the decompression lens;   wherein the real image has a second diameter at the image sensor that is less than the first diameter;   wherein a ratio of the first diameter to the second diameter is between 6.5:1 and 2.3:1; and   wherein the optical system provides a polychromatic modulation transfer function of 30% or more for 150 cy/mm.   
     
     
         2 . The optical system of  claim 1 , wherein the non-parabolic, axially symmetric, aspheric surface of the convex reflector has a hyperbolic shape. 
     
     
         3 . The optical system of  claim 1 , further comprising a hardware aperture positioned to filter out light rays other than those reflected directly from the convex reflector. 
     
     
         4 . The optical system of  claim 3 , wherein the hardware aperture is positioned between the convex reflector and the decompression lens. 
     
     
         5 . The optical system of  claim 1 , wherein the decompression lens includes three or fewer lens elements. 
     
     
         6 . The optical system of  claim 5 , wherein the decompression lens includes two or fewer lens elements. 
     
     
         7 . The optical system of  claim 6 , wherein the decompression lens includes a single lens element having a first aspheric surface and an opposing second aspheric surface, and wherein at least one of the first aspheric surface or the opposing second aspheric surface has a diffractive optical structure disposed thereon. 
     
     
         8 . The optical system of  claim 5 , wherein the decompression lens includes a first negative lens element having a negative optical power, a second negative lens element having a negative optical power, and a positive lens element having a positive optical power and positioned between the first negative lens element and the second negative lens element, wherein the first negative lens element, the second negative lens element, and the positive lens element each have one or more aspheric surfaces. 
     
     
         9 . The optical system of  claim 1 , wherein the first diameter of the convex reflector is at most 32.4 millimeters. 
     
     
         10 . The optical system of  claim 1 , wherein a length of the optical system is at most 60 millimeters. 
     
     
         11 . The optical system of  claim 1 , wherein the optical system is packaged such that the camera has a volume of at most 3 cubic inches or approximately 49.16 cubic centimeters. 
     
     
         12 . The optical system of  claim 1 , wherein the optical system has an effective vertical field of view of at least 70 degrees. 
     
     
         13 . The optical system of  claim 1 , wherein the image sensor has a flat structure or a curved structure. 
     
     
         14 . An optical system for a camera, the optical system comprising:
 a convex reflector having (i) a first diameter and (ii) a non-parabolic surface that provides a virtual curved and compressed image of a scene having a non-parabolic image compression;   a decompression lens positioned to receive the virtual curved and compressed image, the decompression lens configured to:
 decompress the virtual curved and compressed image into a real image having a parabolic image decompression; and 
 project the real image; and 
   an image sensor positioned to receive the real image;   wherein the real image has a second diameter at the image sensor that is less than the first diameter; and   wherein a ratio of the first diameter to the second diameter is between 6.5:1 and 2.3:1.   
     
     
         15 . The optical system of  claim 14 , wherein the first diameter of the convex reflector is at most 32.4 millimeters. 
     
     
         16 . The optical system of  claim 14 , wherein the optical system provides a polychromatic modulation transfer function of 30% or more for 150 cy/mm. 
     
     
         17 . The optical system of  claim 14 , further comprising a hardware aperture (i) spaced a distance from the convex reflector and (ii) positioned between the convex reflector and the decompression lens. 
     
     
         18 . An optical system for a camera, the optical system comprising:
 a housing; and   an optical assembly disposed within the housing, the optical assembly including:
 a convex reflector configured to provide a compressed image of a scene; 
 a decompression lens positioned to receive the compressed image, the decompression lens configured to decompress the compressed image into a decompressed image and project the decompressed image; and 
 an image sensor positioned to receive the decompressed image from the decompression lens; 
   wherein a length of the optical assembly is at most 60 millimeters; and   wherein the housing has a volume of at most approximately 49.16 cubic centimeters.   
     
     
         19 . The optical system of  claim 18 , wherein the convex reflector has a first diameter, the decompressed image has a second diameter at the image sensor that is less than the first diameter, and a ratio of the first diameter to the second diameter is between 6.5:1 and 2.3:1. 
     
     
         20 . The optical system of  claim 18 , wherein the compressed image has a non-parabolic image compression and the decompressed image has a parabolic image decompression.