Zoom optical system and electronic imaging apparatus having the same

Abstract

An electronic imaging apparatus includes a zoom optical system having, in order from the object side, a first lens unit with positive power, a second lens unit with negative power, and an aperture stop, in which the first lens unit is composed of a single positive power unit and the second lens unit has a single negative lens element located at the most object-side position, both surfaces of which are concave, and a positive lens component located at the most image-side position; an electronic image sensor located on the image side of the zoom optical system; and an image processing section electrically processing image data obtained by the electronic image sensor to change the form thereof.

1 . An electronic imaging apparatus comprising: 
 a zoom optical system including, in order from an object side, a first lens unit with positive power, a second lens unit with negative power, and an aperture stop, in which the first lens unit is composed of a single positive power unit and the second lens unit has a single negative lens element located at a most object-side position, both surfaces of which are concave, and a positive lens component located at a most image-side position;    an electronic image sensor located on an image side of the zoom optical system; and    an image processing section electrically processing image data obtained by the electronic image sensor to change a form thereof.    
   
   
       2 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system satisfies the following conditions in focusing of a nearly infinite object point:  
       0.85<| y   07 /( fw ·tan ω 07w )|<0.95  0.75<| y   10 /( fw ·tan ω 10w )|<0.90  
     where y 10  is a maximum image height; y 07  is an image height expressed by multiplying the maximum image height by 0.7; fw is a focal length of an entire zoom optical system at a wide-angle position; ω 07w  is an angle of a ray of light incident on a first surface of a lens unit, corresponding to an image point of the image height y 07  at the wide-angle position, to an optical axis; and ω 10w  low is an angle of a ray of light incident on the first surface of the lens unit, corresponding to an image point of the image height y 10  at the wide-angle position, to the optical axis.  
   
   
       3 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       0.05<| y   07 /( fw ·tan ω 07w )−y 10 /( fw ·tan ω 10w )|<0.15  
     where y 10  is a maximum image height; y 07  is an image height expressed by multiplying the maximum image height by 0.7; fw is a focal length of an entire zoom optical system at a wide-angle position; ω 07w  is an angle of a ray of light incident on a first surface of a lens unit, corresponding to an image point of the image height y 07  at the wide-angle position, to an optical axis; and ω 10w  is an angle of a ray of light incident on the first surface of the lens unit, corresponding to an image point of the image height y 10  at the wide-angle position, to the optical axis.  
   
   
       4 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       0.5<( R 21 +R 22)/( R 21 −R 22)<0.95  
     where R21 is a radius of curvature of an object-side surface of the single negative lens element in the second lens unit and R22 is a radius of curvature of an image-side surface of the single negative lens element in the second lens unit.  
   
   
       5 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       n dA2 >1.70  
     where n dA2 is a refractive index, relating to the d line, of the single negative lens element in the second lens unit.    
   
   
       6 . An electronic imaging apparatus according to  claim 1 , satisfying the following condition:  
       ft/fw>4  
     where ft is a focal length of an entire zoom optical system at a telephoto position and fw is a focal length of the entire zoom optical system at a wide-angle position.  
   
   
       7 . An electronic imaging apparatus according to  claim 1 , satisfying the following condition:  
       −0.90<( R 23 +R 24)/( R 23 −R 24)<−0.20  
     where R23 is a radius of curvature of a most object-side surface of the positive lens component in the second lens unit and R24 is a radius of curvature of a most image-side surface of the positive lens component in the second lens unit.  
   
   
       8 . An electronic imaging apparatus according to  claim 1 , satisfying the following condition:  
       0.6<(β2 t/β 2 w )/(β3 t/β 3 w )<1.2  
     where β2t is a magnification of the second lens unit at a telephoto position, β2w is a magnification of the second lens unit at a wide-angle position, β3t is a magnification of a third lens unit at the telephoto position, and β3w is a magnification of the third lens unit at the wide-angle position.  
   
   
       9 . An electronic imaging apparatus according to  claim 1 , wherein the second lens unit includes, in order from the object side, the single negative lens element whose both surfaces are concave, a single negative lens element, and the positive lens component.  
   
   
       10 . An electronic imaging apparatus according to  claim 1 , satisfying the following condition:  
       0.2<( LT−LW )/( DT−DW )<1.1  
     where LT is a total length of the zoom optical system at a telephoto position, LW is a total length of the zoom optical system at a wide-angle position, DT is a spacing between the first lens unit and the second lens unit at the telephoto position, and DW is a spacing between the first lens unit and the second lens unit at the wide-angle position.  
   
   
       11 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system comprises, in order from the object side, the first lens unit with positive power, the second lens unit with negative power, the aperture stop, a third lens unit with positive power, and a fourth lens unit with positive power, and upon zooming from a wide-angle region to a telephoto region, at least, a spacing between the first lens unit and the second lens unit is widened, a spacing between the second lens unit and the third lens unit is narrowed, and a spacing between the third lens unit and the fourth lens unit is widened.  
   
   
       12 . An electronic imaging apparatus according to  claim 11 , wherein the second lens unit and the third lens unit have a positive lens component and a negative lens component, respectively.  
   
   
       13 . An electronic imaging apparatus according to  claim 1 , wherein the zoom optical system comprises, in order from the object side, the first lens unit with positive power, the second lens unit with negative power, the aperture stop, a third lens unit with positive power, and a fourth lens unit with positive power, and upon zooming from a wide-angle region to a telephoto region, a spacing between the first lens unit and the second lens unit is widened, a spacing between the second lens unit and the third lens unit is narrowed, a spacing between the third lens unit and the fourth lens unit is widened, a spacing between the fourth lens unit and the electronic image sensor is changed, and the stop is moved integrally with the third lens unit.  
   
   
       14 . An electronic imaging apparatus according to  claim 11 , wherein the fourth lens unit is a single positive lens element.  
   
   
       15 . An electronic imaging apparatus comprising: 
 a zoom optical system including, in order from an object side, a first lens unit with positive refracting power and a second lens unit with negative refracting power;    an electronic image sensor located on an image side of the zoom optical system; and    an image processing section electronically processing image data obtained by the electronic image sensor to change a form thereof,    wherein the first lens unit has, in order from the object side, a single negative lens element whose both surfaces are concave, a reflecting member, and a single positive lens component.    
   
   
       16 . An electronic imaging apparatus according to  claim 15 , wherein the zoom optical system satisfies the following conditions in focusing of a nearly infinite object point:  
       0.85<| y   07 /( fw ·tan ω 07w )|<0.97  0.75<| y   10 /( fw ·tan ω 10w )|<0.92  
     where y 10  is a maximum image height; y 07  is an image height expressed by multiplying the maximum image height by 0.7; fw is a focal length of an entire zoom optical system at a wide-angle position; ω 07w  is an angle of a ray of light incident on a first surface of a lens unit, corresponding to an image point of the image height y 07  at the wide-angle position, to an optical axis; and ω 10w  is an angle of a ray of light incident on the first surface of the lens unit, corresponding to an image point of the image height y 10  at the wide-angle position, to the optical axis.  
   
   
       17 . An electronic imaging apparatus according to  claim 15 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       0.02<| y   07 /( fw ·tan ω 07w )− y   10 /( fw ·tan ω 10w )|<0.15  
     where y 10  is a maximum image height; y 07  is an image height expressed by multiplying the maximum image height by 0.7; fw is a focal length of an entire zoom optical system at a wide-angle position; ω 07w  is an angle of a ray of light incident on a first surface of a lens unit, corresponding to an image point of the image height y 07  at the wide-angle position, to an optical axis; and ω 10w  is an angle of a ray of light incident on the first surface of the lens unit, corresponding to an image point of the image height y 10  at the wide-angle position, to the optical axis.  
   
   
       18 . An electronic imaging apparatus according to  claim 15 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       0.33<( R 11 +R 12)/( R 11 −R 12)<0.82  
     where R11 is a radius of curvature, measured along an optical axis, of an object-side surface of the single negative lens element and R12 is a radius of curvature, measured along the optical axis, of an image-side surface of the single negative lens element.  
   
   
       19 . An electronic imaging apparatus according to  claim 15 , wherein the zoom optical system satisfies the following condition in focusing of a nearly infinite object point:  
       n dA1 >1.70  
     where n dA1  is a refractive index, relating to the d line, of the single negative lens element.  
   
   
       20 . A zoom optical system comprising, in order from an object side: 
 a first lens unit with positive refracting power; and    a second lens unit with negative refracting power;    wherein the first lens unit has, in order from the object side, a single negative lens element whose both surfaces are concave, a reflecting member, and a single positive lens element.    
   
   
       21 . A zoom optical system according to  claim 20 , wherein the single positive lens component in the first lens is a single biconvex positive lens element.  
   
   
       22 . An electronic imaging apparatus comprising: 
 a zoom optical system according to  claim 20;     an electronic image sensor located on an image side of the zoom optical system; and    an image processing section electrically processing image data obtained by the electronic image sensor to change a form thereof.    
   
   
       23 . An electronic imaging apparatus according to  claim 15 , satisfying the following condition:  
       −3 <f   1   /fw<− 0.5  
     where f 1  is a focal length of the first lens unit and fw is a focal length of an entire zoom optical system at a wide-angle position.  
   
   
       24 . A zoom optical system according to  claim 20 , satisfying the following condition:  
       −3 <f   1   /fw<− 0.5  
     where f 1  is a focal length of the first lens unit and fw is a focal length of an entire zoom optical system at a wide-angle position.  
   
   
       25 . An electronic imaging apparatus according to  claim 15 , wherein the zoom optical system comprises, in order from the object side, the first lens unit with positive refracting power, the second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with positive refracting power, and upon zooming from a wide-angle position to a telephoto position, the first lens unit is fixed with respect to an image plane, the second lens unit is moved toward the image side, the third lens unit is fixed, and the fourth lens unit is moved toward the object side.  
   
   
       26 . A zoom optical system according to  claim 20 , comprising, in order from the object side, the first lens unit with positive refracting power, the second lens unit with negative refracting power, a third lens unit with positive refracting power, and a fourth lens unit with positive refracting power, wherein upon zooming from a wide-angle position to a telephoto position, the first lens unit is fixed with respect to an image plane, the second lens unit is moved toward an image side, the third lens unit is fixed, and the fourth lens unit is moved toward the object side.