Imaging device, focusing method and program

Abstract

An image processing circuit/CPU performs AF processing in response to a halfway shutter operation and upon confirmation of a shooting shutter instruction causes the light emitting means in a flash circuit to emit light, and decides the amount of light emitted at shooting time on the basis of the brightness component of an output signal of an imaging element, whereby a subject distance is calculated from the amount of light emitted at shooting time, wherein, when the in-focus decision in the AF processing is negative, an optical lens is moved by a lens drive circuit to the position corresponding to the subject distance which has been acquired on the basis of the amount of light emitted at shooting time and a shooting operation is then performed.

1 . An imaging device having a moving unit configured to move an optical system and a decision unit configured to decide a position to which the optical system is to be moved by the moving unit so that a subject is brought into focus, comprising: 
 a light emitting unit;    a light control unit which determines a proper amount of light at shooting time emitted by the light emitting unit based on brightness of the subject when the light emitting unit is caused to make preliminary emission;    a distance acquisition unit which acquires a subject distance to the subject corresponding to the brightness of the subject when preliminary light emission is made by the light emitting unit to allow the light control unit to determine a proper amount of light; and    a control unit which, when the decision unit cannot decide the position to which the optical system is to be moved, controls the moving unit so that the optical system is moved to the position corresponding to the subject distance acquired by the distance acquisition unit.    
   
   
       2 . An imaging device according to  claim 1 , wherein the distance acquisition unit acquires the subject distance based on the proper amount of light determined by the light control unit.  
   
   
       3 . A focusing method in an imaging device having an autofocus function which decides a position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines a proper light emission time at shooting time of a light emission unit based on brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light only for the proper light emission time at shooting time, which comprises: 
 moving the optical system, when the position to which the optical system is to be moved cannot be decided by the autofocus function, to the position corresponding to the subject distance corresponding to the brightness of the subject when the light emission unit is caused to make preliminary light emission by the light control function.    
   
   
       4 . A computer for use with an imaging device which has an autofocus function which decides a position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines a proper light emission time duration at a shooting time of a light emission unit based on brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light only for the proper light emission time duration at the shooting time, wherein the computer operates on a program for causing the computer to perform a function as control means which, when the position to which the optical system is to be moved cannot be decided by the autofocus function, moves the optical system to the position corresponding to the subject distance corresponding to the brightness of the subject when the light emission unit is caused to make preliminary light emission by the light control function.  
   
   
       5 . An imaging device having moving means for moving an optical system and decision means for deciding a position to which the optical system is to be moved by the moving means so that a subject is brought into focus, comprising: 
 light emitting means;    light control means which determines a proper amount of light at shooting time emitted by the light emitting means based on brightness of the subject when the light emitting means is caused to make preliminary emission;    distance acquisition means which acquires a subject distance to the subject corresponding to the brightness of the subject when preliminary light emission is made by the light emitting means to allow the light control means to determine the proper amount of light; and    nullifying means which, when a relationship between the position decided by the decision means and the position acquired by the distance acquisition means meets a predetermined condition, nullifies the decision by the decision means.    
   
   
       6 . An imaging device according to  claim 5 , wherein the distance acquisition means acquires the subject distance based on the proper amount of light determined by the light control means.  
   
   
       7 . An imaging device according to  claim 5  or  claim 6 , wherein the nullifying means nullifies the position to which the optical system is to be moved decided by the decision means and changes the position to which the optical system is to be moved at shooting time to the position corresponding to the subject distance acquired by the distance acquisition means.  
   
   
       8 . An imaging device according to  claim 5  or  claim 6 , wherein the predetermined condition is that the difference between the subject distance corresponding to the position to which the optical system is to be moved decided by the decision means and the subject distance acquired by the distance acquisition means is smaller than a predetermined value.  
   
   
       9 . A focusing method for use with an imaging device having an autofocus function which decides the position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines the proper light emission time at shooting time of a light emission unit on the basis of the brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light at shooting time only for the proper light emission time, the focusing method comprising: 
 making a decision of whether or not the relationship between the subject distance corresponding to the position to which the optical system is to be moved decided by the autofocus function and the subject distance corresponding to the brightness of the subject when the light emission unit is caused by the light control function to make preliminary light emission meets a predetermined condition; and    nullifying the position to which the optical system is to be moved decided by the autofocus function when the predetermined condition is met.    
   
   
       10 . A computer provided in an imaging device having an autofocus function which decides the position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines the proper light emission time at shooting time of a light emission unit on the basis of the brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light at shooting time only for the proper light emission time, the computer operating on a program for performing the functions of: 
 making a decision of whether or not the relationship between the subject distance corresponding to the position to which the optical system is to be moved decided by the autofocus function and the subject distance corresponding to the brightness of the subject when the light emission unit is caused by the light control function to make preliminary light emission meets a predetermined condition; and    nullifying the position to which the optical system is to be moved decided by the autofocus function when the predetermined condition is met.    
   
   
       11 . An imaging device having moving means for moving an optical system and decision means for deciding a position to which the optical system is to be moved by the moving means so that a subject is brought into focus, comprising: 
 light emitting means;    light control means which determines a proper amount of light at shooting time emitted by the light emitting means based on brightness of the subject when the light emitting means is caused to make preliminary light emission;    distance acquisition means which acquires a subject distance to the subject corresponding to the brightness of the subject when preliminary light emission is made by the light emitting means;    measurement means which measures the brightness of the subject under a shooting standby condition; and    control means which, when the brightness of the subject measured by the measurement means is lower than a predetermined value, controls the moving means so that the optical system is moved to a position corresponding to the subject distance acquired by the distance acquisition means without depending on the decision means.    
   
   
       12 . An imaging device according to  claim 11 , wherein the distance acquisition means acquires the subject distance on the basis of the proper amount of light determined by the light control means.  
   
   
       13 . A focusing method for use with an imaging device having an autofocus function which decides the position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines the proper light emission time at shooting time of a light emission unit on the basis of the brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light at shooting time only for the proper light emission time, the focusing method comprising: 
 measuring the brightness of the subject under a shooting standby condition;    making a decision of whether or not the brightness of the subject measured by the measurement step is lower than a predetermined value; and    moving the optical system at shooting time to the position corresponding to the subject distance corresponding to the brightness of the subject when the light emission means is caused to make preliminary light emission without depending on the autofocus function when the decision is that the brightness of the subject measured by the measurement step is lower than the predetermined value.    
   
   
       14 . A computer provided in an imaging device having an autofocus function which decides a position to which an optical system is to be moved so that a subject is brought into focus and a light control function which determines a proper light emission time at shooting time of a light emission unit based on brightness of the subject when preliminary light emission is made and then causes the light emission unit to emit light at shooting time only for the proper light emission time, a computer operating on a program for performing the functions of: 
 measuring the brightness of the subject under a shooting standby condition; and    moving the optical system at shooting time to a position corresponding to the subject distance corresponding to the brightness of the subject when the light emission means is caused to make preliminary light emission without depending on the autofocus function when the brightness of the subject is decided by the measuring function to be lower than a predetermined value.    
   
   
       15 . An imaging device having moving means for moving an optical system and decision means for deciding a position to which the optical system is to be moved by the moving means so that a subject is brought into focus, comprising: 
 light emitting means;    light control means which determines a proper amount of light at shooting time emitted by the light emitting means based on brightness of the subject when the light emitting means is caused to make preliminary emission;    distance acquisition means which acquires a subject distance to the subject corresponding to the brightness of the subject when preliminary light emission is made by the light emitting means to allow the light control means to determine a proper amount of light; and    control means which, when the decision means cannot decide the position to which the optical system is to be moved, controls the moving means so that the optical system is moved to the position corresponding to the subject distance acquired by the distance acquisition means.