Lens optical unit and imaging device

Abstract

Provided is a lens optical unit, including at least one lens arranged at an object side of a solid-state image sensor. An imaging plane of the image sensor has a non-planar shape causing a sag amount in an optical axis direction to increase as a distance from an optical axis increases, and satisfies the expression: ρ×Sag>0, where ρ represents a Petzval curvature of an optical unit represented by ρ  :  ρ = ∑ k  1 r k · ( 1 n k ′ - 1 n k ) , r k represents a curvature radius of a k th lens surface from the object side, n k represents a refractive index of a medium before being incident to the k th lens surface from the object side, n′ k represents a refractive index of a medium after being emitted from the k th lens surface from the object side, and Sag represents a sag amount in the optical axis direction related to a given point other than the optical axis on the imaging plane.

What is claimed is: 
     
         1 . A lens optical unit, comprising:
 at least one lens, arranged at an object side of a solid-state image sensor, wherein   an imaging plane of the solid-state image sensor is closest to an image side, convex toward the image side and has a non-planar shape that causes a distance to the object side in an optical axis direction to decrease as a distance from an optical axis increases.   
     
     
         2 . The lens optical unit according to  claim 1 , wherein
 a conditional expression (1) is satisfied:
   ρ<0  (1)
 
   where ρ represents a Petzval curvature of an optical unit represented by ρ:   
       
         
           
             
               ρ 
               = 
               
                 
                   ∑ 
                   k 
                   
                       
                   
                 
                  
                 
                   
                     1 
                     
                       r 
                       k 
                     
                   
                   · 
                   
                     ( 
                     
                       
                         1 
                         
                           n 
                           k 
                           ′ 
                         
                       
                       - 
                       
                         1 
                         
                           n 
                           k 
                         
                       
                     
                     ) 
                   
                 
               
             
           
         
       
     
     
         3 . The lens optical unit according to  claim 1 , wherein
 the non-planar shape of the imaging plane in the solid-state image sensor is a curved surface shape that is rotationally symmetric around the optical axis.   
     
     
         4 . The lens optical unit according to  claim 1 , wherein
 an angle at which a main light ray having a maximum angle of field is incident to the imaging plane in a state of shooting at infinity in an entire zoom area satisfies a conditional expression (2):
   θ max <45°  (2)
 
   where θ max  represents an angle at which a main light ray having a maximum angle of field is incident to the imaging plane.   
     
     
         5 . The lens optical unit according to  claim 3 , wherein
 the entire imaging plane of the solid-state image sensor has a spherical shape with the same curvature.   
     
     
         6 . The lens optical unit according to  claim 1 , wherein
 the imaging plane of the solid-state image sensor and a focal length of the optical unit satisfy a conditional expression (3):
   −5.0< R   img   /f   inf <−1.0  (3)
 
   where R img  represents a focal length of the optical unit at the time of focusing at infinity.   
     
     
         7 . The lens optical unit according to  claim 1 , wherein
 a total of four lenses including two positive lenses and two negative lenses are arranged as the lens.   
     
     
         8 . The lens optical unit according to  claim 1 , wherein
 a lens closest to an image side is a concave meniscus lens having a shape which is convex toward the image side.   
     
     
         9 . The lens optical unit according to  claim 1 , wherein
 an aspheric surface is formed on a lens surface closest to the image side.   
     
     
         10 . An imaging device, comprising:
 a lens optical unit; and   a solid-state image sensor that converts an optical image formed by the lens optical unit into an electrical signal; wherein   the lens optical unit includes at least one lens, arranged at an object side of the solid-state image sensor,   an imaging plane of the solid-state image sensor is closest to an image side, convex toward the image side and has a non-planar shape that causes a distance to the object side in an optical axis direction to decrease as a distance from an optical axis increases.   
     
     
         11 . The imaging device according to  claim 10 , further comprising:
 an imaging processing unit.   
     
     
         12 . The imaging device according to  claim 11 , wherein
 the imaging processing unit performs a compression coding and decompression decoding process of an image signal.   
     
     
         13 . The imaging device according to  claim 10 , further comprising:
 a camera signal processing unit configured to perform signal processing, including converting an output signal from the image sensor into a digital signal, a noise reduction signal, an image quality correction signal or a brightness or color-difference signal.   
     
     
         14 . The imaging device according to  claim 10 , further comprising:
 a display configured to display an image captured by the image sensor.   
     
     
         15 . The imaging device according to  claim 10 , further comprising:
 an input unit performing shutter release.