Imaging system where a quick return mirror is returned to a down state and a stop is returned to a fully open state before the accumulation period ends

Abstract

An apparatus has an image sensing device, and a signal processing device for performing a first image sensing operation for making the image sensing device perform an image sensing operation in an exposure state to obtain a sensed image signal, and a second image sensing operation for making the image sensing device perform an image sensing operation in a non-exposure state to obtain a sensed image signal, and processing the sensed image signal obtained by the first image sensing operation by the sensed image signal obtained by the second image sensing operation. The signal processing device determines in accordance with the image sensing time of the first image sensing operation whether or not the second image sensing operation is performed.

What is claimed is: 
     
       1. An image taking apparatus comprising:
 (i) a charge accumulation type image sensing element on which an optical image of an object image is formed; 
 (ii) a shutter which adjusts an exposure time of said image sensing element; 
 (iii) a quick return mirror which operates to an up state where input light is guided to said image sensing element and down state where input light is guided to a finder; and 
 (iv) a controller which controls 
 (a) when image sensing in a case where an image sensing process is started, said quick return mirror is placed in moved to the up state and the a stop is driven; subsequently, said image sensing element is cleared of electric charge and charge accumulation in said image sensing element is started; the then, said shutter is opened and exposure of said image sensing element begins is begun, and 
 (b) when image sensing is complete in a case where the image sensing process is completed, said shutter is closed; subsequently, the stop is opened and said quick return mirror is placed in moved to the down state; then, it is determined whether or not a predetermined amount of charge accumulation time by said image sensing element has elapsed; subsequently, if it is determined that the predetermined amount of time has elapsed, charge accumulation of said image sensing element is completed and then a readout operation of electric charge signals from said image sensing element is carried out. 
 
     
     
       2. A control method of an image taking apparatus comprising a charge accumulation type image sensing element on which an optical image of an object is formed, a shutter which adjusts an exposure time of said image sensing element; and a quick return mirror which operates to an up state where input light is guided to said image sensing element and down state where input light is guided to a finder, the method comprising the steps of:
 when image sensing isin a case where an image sensing process is controlled to be started, placingmoving said quick return mirror into said up state and driving saida stop; subsequently, clearing said image sensing elements of electric charge and starting charge accumulation in said image sensing element, and then opening said shutter and beginning exposure of said image sensing element; 
 when image sensing isin a case where the image sensing process is controlled to be completed, driving said shutter to close, and subsequently adriving said stop to open and moving said quick return mirror to the down state, then determining whether or not a predetermined amount of charge accumulation time by said image sensing element ishas elapsed, and if said predetermined charge accumulationamount of time by said image sensing element has elapsed, subsequently completing charge accumulation of said image sensing elements element and then carrying out a readout operation of electric charge signals from said image sensing element. 
 
     
     
       3. An image taking apparatus comprising:
 (i) a charge accumulation type image sensing element on which an optical image of an object image is formed;   (ii) a shutter which adjusts an exposure time of said image sensing element;   (iii) a quick return mirror which operates to an up state where input light is guided to said image sensing element and down state where input light is guided to a finder; and   (iv) a controller which controls
 (a) in a case where an image sensing process is started, said quick return mirror is moved to the up state and a stop is driven; subsequently, electric charge of said image sensing element is cleared and charge accumulation in said image sensing element is started; then, said shutter is opened and exposure of said image sensing element is begun, and 
 (b) in a case where the image sensing process is complete, said shutter is closed; subsequently, said stop is opened and said quick return mirror is moved to the down state; subsequently, if a predetermined charge accumulation time of said image sensing element has elapsed, charge accumulation of said image sensing element is completed and then a readout operation of electric charge signals from said image sensing element is carried out. 
   
     
     
       4. A control method of an image taking apparatus comprising a charge accumulation type image sensing element on which an optical image of an object is formed, a shutter which adjusts an exposure time of said image sensing element; and a quick return mirror which operates to an up state where input light is guided to said image sensing element and down state where input light is guided to a finder, the method comprising the steps of:
 in a case where an image sensing process is controlled to be started, moving said quick return mirror to the up state and driving a stop; subsequently, clearing electric charge of said image sensing element and starting charge accumulation in said image sensing element, and then opening said shutter and beginning exposure of said image sensing element;   in a case where the image sensing is controlled to be completed, closing said shutter, and subsequently opening said stop and moving said quick return mirror to the down state, subsequently if a predetermined charge accumulation time of said image sensing element has elapsed, completing charge accumulation of said image sensing element and then carrying out a readout operation of electric charge signals from said image sensing element.