Lens with external aperture stop

Abstract

A lens assembly particularly suited to use with high resolution digital cameras and other portable electronic devices. The lens includes a positive powered front group having one or two elements and a second, aberration correcting, rear group having in order from the front a bi-concave element, a meniscus element and a bi-concave element. The aperture stop plane is just in front of the front group. A combined operator and shutter device is positioned at the aperture stop plane. All of the lens elements are made of glass and have spherical surfaces.An objective lens for use in a digital camera or cell phone having a camera body, the lens having a sensor such as a CCD providing an active surface that serves as a focal plane, a digital image corresponding to a varying light image falling on the focal plane, a lens assembly for forming the varying light image, the lens assembly comprising a positive doublet having a first and a second element or a singlet, at the object end of the lens assembly followed by a lens element group spaced from the positive doublet or alternatively, a positive singlet and having three elements, in order from the object end, a bi- concave element, a meniscus element and a bi - convex element, and an aperture stop located at a predetermined distance in front of the positive doublet or positive singlet lens element at the object end of the lens assembly.

1. A compact lens assembly which comprises:
 a first, positively-powered, lens element group at a distal assembly end, said positively-powered group having from one to two elements;  
 a second lens element group spaced proximally from said first lens element group and having three elements, in under from said distal end, a bi-concave element, a meniscus element and a bi-convex element;  
 said lens assembly having an aperture stop located adjacent to said distal end of said lens at a predetermined distance therefrom; and  
 said aperture stop comprising a combined variable aperture and shutter assembly at said predetermined aperture stop location.  
 
     
     
       2. The compact lens assembly according to  claim 1  wherein all of said elements have spherical surfaces. 
     
     
       3. The compact lens assembly according to  claim 1  wherein all of said elements are formed from glass. 
     
     
       4. The compact lens assembly according to  claim 1  wherein said lens assembly has a focal length of about 4.5 mm and an overall length from said aperture stop to an image plane is about 8 mm. 
     
     
       5. The compact lens assembly according to  claim 1  wherein said first group consists of a single bi-convex element. 
     
     
       6. The compact lens assembly according to  claim 1  wherein said first group is an achromatic doublet having bi-convex outer surfaces. 
     
     
       7. The compact lens assembly according to  claim 1  wherein the lens assembly satisfies the following data:
                                       Surface   Axial   Index Of   Abbe         Radius   Distance   Refraction   Number     Element   SURFACE   AXIAL   INDEX OF   ABBE     ELEMENT   RADIUS   DISTANCE   REFRACTION   NUMBER                                       22 Aperture       0.019358679             Stop     14, R1   3.8630600   0.97497407   1.85544   36.59     14, R2   −10.949689   0.41938736     16, R3   −3.5840039   0.70701838   1.91761   21.51     16, R4   5.5340363   0.33068768     18, R5   −6.0461650   1.2803852   1.80279   46.76     18, R6   −2.8591050   0.0     20, R7   6.2365452   1.3698834   1.71300   53.83     20, R8   −26.474757   2.9640898                                               
 wherein the listed elements and surfaces are numbered from the distal end of said lens assembly.  
 
     
     
       8. The compact lens assembly according to  claim 1  wherein the lens assembly satisfies the following data:
                                           AXIAL   INDEX OF   ABBE     ELEMENT   RADIUS   DISTANCE   REFRACTION   NUMBER                                       42 Aperture       .069231426             Stop     32, R1   44.530099   .74988524   1.60342   38.01     32, R2   3.6015366   1.8820225     34, R3   3.5015366   0.0   1.85584   36.59     34, R4   −10.775653   .8438336     36, R5   −4.0121198   .7499969   1.76182   26.55     36, R6   14.319591   .72626772     38, R7   −7.5483354   1.0981703   1.45950   57.35     38, R8   −4.3839072   .049998691     40, R9   52.604912   1.5000000   1.64050   60.10     40, R10   −8.4658891   3.0506764                                               
 wherein the listed elements and surfaces are numbered from the distal end of said lens assembly.  
 
     
     
       9. In a digital camera having a camera body, a sensor for forming a digital image corresponding to a varying light image falling thereon, a lens for forming said light image, a variable aperture for varying the light image intensity and a shutter for shielding the sensor during a digital image read-out from said sensor, the improvement comprising:
 said lens having four to five elements extending from a distal end to a proximal end adjacent to said sensor and comprising: a first, positively-powered, lens element group at said a distal end, said positively-powered group having from one to two elements;    a second lens element group spaced from said first lens element group an having three elements, in order from said distal end, a bi-concave element, a meniscus element and a bi-convex element;    all of said elements being spherical and formed from glass; and    
 said lens assembly having an aperture stop located adjacent to said distal end of said lens at a predetermined distance therefrom; and  
 said aperture stop comprising a combined variable aperture and shutter assembly at said predetermined aperture stop location.  
 
     
     
       10. The improvement according to  claim 9  wherein said lens assembly has a focal length of about 4.5 mm and an overall length from said aperture stop to an image plane is about 8 mm. 
     
     
       11. The improvement according to  claim 9  wherein said first group consists of a single bi-convex element. 
     
     
       12. The improvement according to  claim 9  wherein said first group is an achromatic doublet having bi-convex outer surfaces. 
     
     
       13. The compact lens assembly according to  claim 9  wherein the lens assembly satisfies the following data:
                                           AXIAL   INDEX OF   ABBE     ELEMENT   RADIUS   DISTANCE   REFRACTION   NUMBER                                       42 Aperture       .069231426             Stop     32, R1   44.530099   .74988524   1.60342   38.01     32, R2   3.6015366   1.8820225     34, R3   3.6015366   0.0   1.85544   36.59     34, R4   −10.775653   .8438336     36, R5   −4.0121198   .7499969   1.76182   26.55     36, R6   14.319591   .72626772     38, R7   −7.5483354   1.0981703   1.65950   57.35     38, R8   −4.3839072   .049998691     40, R9   52.604912   1.5000000   1.64050   60.10     40, R10   −8.4658891   3.0506766             22 Aperture       0.019358679     Stop     14, R1       3.8630600   0.97497407   1.85544   36.59     14, R2   −10.949689   0.41938736     16, R3   −3.5840039   0.70701838   1.91761   21.51     16, R4       5.5340363   0.33068768     18, R5   −6.0461650    1.2803852   1.80279   46.76     18, R6   −2.8591050          0.0     20, R7       6.2365452    1.3698834   1.71300   53.83     20, R8   −26.474757    2.9640898                                                         
 wherein the listed elements and surfaces are numbered from the distal end of said lens assembly.  
 
     
     
       14. The compact lens assembly according to  claim 9  wherein the lens assembly satisfies the following data:
                                           AXIAL   INDEX OF   ABBE     ELEMENT   RADIUS   DISTANCE   REFRACTION   NUMBER                                       42 Aperture       .069231426             Stop     32, R1   44.530099   .74988524   1.60342   38.01     32, R2   3.6015366   1.8820225     34, R3   3.6015366   0.0   1.85544   36.59     34, R4   −10.775653   .8438336     36, R5   −4.0121198   .7499969   1.76182   26.55     36, R6   14.319591   .72626772     38, R7   −7.5483354   1.0981703   1.65950   57.35     38, R8   −4.3839072   .049998691     40, R9   52.604912   1.5000000   1.64050   60.10     40, R10   −8.4658891   3.0506766                                               
 wherein the listed elements and surfaces are numbered from the distal end of said lens assembly.  
 
     
     
       15. A compact lens assembly which comprises:
   a positive lens element at the object end of the lens assembly,        a lens element group spaced proximally from the positive lens element and having three elements, in order from the object end,        a bi - concave element formed from an optical material having an Abbe value of about  21 . 5 ,        a meniscus element and        a bi - convex element,        the lens assembly having an aperture stop located between the object and the positive lens element, adjacent to the object end of the lens assembly at a        predetermined distance therefrom.     
     
     
       16. The compact lens assembly of  claim 15  wherein the positive lens element and the elements in the lens element group are positioned and formed to obtain a field of view of ± 30  degrees with a relative aperture as large as f/ 2 . 8 . 
     
     
       17. A compact lens assembly which comprises:
   a positive lens element having an index of refraction of about  1 . 85  at the object end of the lens assembly,        a lens element group spaced proximally from the positive lens element and having three elements, in order from the object end,        a bi - concave element formed from an optical material having an Abbe value not exceeding  27 ,        a meniscus element and        a bi - convex element,        the lens assembly having an aperture stop located between the object and the positive lens element, adjacent to the object end of the lens assembly at a predetermined distance therefrom.     
     
     
       18. A digital camera having:
   a camera body,        a sensor for forming a digital image corresponding to a varying light image falling thereon, and        a compact lens assembly for forming the light image comprising:      a positive lens element at the object end of the lens assembly,        a lens element group spaced proximally from the positive lens element and having three elements, in order from the object end,        a bi - concave element formed from an optical material having an an Abbe value of about  21 . 5 ,        a meniscus element and        a bi - convex element,          the compact lens assembly having an aperture stop located between the object and the positive lens element, adjacent to the object end of the lens assembly at a predetermined distance therefrom, the positive lens element and the elements in the lens element group being positioned and formed to obtain an image of the object on the sensor.     
     
     
       19. A digital camera having:
   a camera body,        a sensor for forming a digital image corresponding to a varying light image falling thereon, and        a compact lens assembly for forming the light image comprising:      a positive lens element having an index of refraction of about  1 . 85  at the object end of the lens assembly,        a lens element group spaced proximally from the positive lens element and having three elements, in order from the object end,        a bi - concave element formed from an optical material having an Abbe value not exceeding  27 ,        a meniscus element and        a bi - convex element,          the compact lens assembly having an aperture stop located between the object and the positive lens element, adjacent to the object end of the lens assembly at a predetermined distance therefrom, the positive lens element and the elements in the lens element group being positioned and formed to obtain an image of the object on the sensor.     
     
     
       20. A lens assembly receiving light from an object through an aperture stop, the lens assembly extending from the aperture stop at the object end to an image end adjacent to a sensor, the lens assembly comprising:
   a positive doublet having a first and a second element at the object end of the lens assembly;        a lens element group spaced from the positive doublet and having three elements, in order from the object end,        a bi - concave element,        a meniscus element and        a bi - convex element;        the aperture stop being located between the object and the positive doublet, adjacent to the object end of the lens assembly at a predetermined distance therefrom.     
     
     
       21. The compact lens assembly of  claim 20     wherein the bi - concave element is formed from an optical material having an Abbe value not exceeding  27 .     
     
     
       22. The compact lens assembly of  claim 20     wherein the bi - concave element is formed from an optical material having an Abbe value of about  26 . 55 .     
     
     
       23. The compact lens assembly of  claim 20  wherein the positive element of the doublet is formed from an optical material having an index of refraction of at least  1 . 78 . 
     
     
       24. The compact lens assembly of  claim 20  wherein the positive element of the doublet is formed from an optical material having an index of refraction of about  1 . 85 . 
     
     
       25. The compact lens assembly of  claim 20  wherein the positive doublet and the elements in the lens element group are positioned and formed to obtain an image over a field of view of ± 27  degrees. 
     
     
       26. In a digital camera having:
   a camera body,        a sensor for forming a digital image corresponding to a varying a light image falling thereon,        a lens assembly for forming the varying light image, the lens assembly comprising:      a positive doublet having a first and a second element at the object end of the lens assembly;        a lens element group spaced from the positive doublet and having three elements, in order from the object end,        a bi - concave element,        a meniscus element and        a bi -  convex element;          the aperture stop being located between the object and the positive doublet, adjacent to the object end of the lens assembly at a predetermined distance therefrom.     
     
     
       27. The lens assembly of  claim 26  wherein the bi- concave element is formed from an optical material having an Abbe value not exceeding  27 .   
     
     
       28. The compact lens assembly of  claim 26  wherein the bi- concave element is formed from an optical material having an Abbe value of about  26 . 55 .   
     
     
       29. The compact lens assembly of  claim 26  wherein the positive element of the doublet is formed from an optical material having an index of refraction of at least  1 . 78 . 
     
     
       30. The compact lens assembly of  claim 26  wherein the positive element of the doublet is formed from an optical material having an index of refraction of about  1 . 85 . 
     
     
       31. The compact lens assembly of  claim 26  wherein the positive doublet and the elements in the lens element group are positioned and formed to obtain an image over a field of view of ± 27  degrees.