Abstract:
A digital camera including a focus control mechanism for focusing the camera on a subject of the present invention includes a first and a second selector. The first selector selects either one of a first and a second pickup mode assigned to a still picture and a movie, respectively. The second selector selects either one of a first focus range advantageous for normal-range pickup and a second focus range assigned to a subject positioned in a range shorter than the first focus range. A controller causes, in the first pickup mode, the focus control mechanism to operate in the focus range selected by the second selector or causes, in the second pickup mode, the above mechanism to operated in a range including the first focus range without regard to the focus range selected by the second selector.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a digital camera capable of selectively picking up a desired subject in the form of a still picture or a movie and an automatic focusing method for the same.  
           [0003]    2. Description of the Background Art  
           [0004]    A digital camera operable in a macro mode for picking up a subject positioned within a short range of one meter or less is conventional. In the macro mode, a focus scanning or search range in, e.g., a range-scanning or search system is set in a short range in order to focus a digital camera on a desired subject lain in a short range more rapidly than in a normal mode. In the range-scanning system, the focus of a lens system is varied from a short distance to an object to infinity, and then focusing on the object is detected while determining which of the pictures presents the highest sharpness. However, a digital camera operable in the macro mode in both of a still picture mode and a movie mode has a problem that the macro mode must be selected even in the movie mode when a desired subject lies in a short range. Moreover, in the movie mode, because the range to the subject is not always constant, the macro mode makes it difficult to advantageously adjust the focus throughout the movie mode operation when selected.  
           [0005]    Japanese patent laid-open publication No. 164606/1998, for example, discloses a digital camera selectively operable in a movie or a still picture mode and advantageous for short-range pickup. More specifically, this digital camera is constructed to determine, when the movie mode is selected, whether or not a desired subject lies in a short range and automatically replaces, if the subject lies in a short range, the movie mode with the still picture mode. This, however, prevents the subject lying in a short range to be desirably picked up in the movie mode.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to provide a digital camera allowing the operator of the camera to pickup a short-range subject in a movie mode without caring about a macro mode and maintaining the movie mode, and an automatic focusing method for the same.  
           [0007]    In accordance with the present invention, a digital camera including a focus control mechanism for focusing the camera on a subject includes a first selecting circuit configured to select either one of a first and a second pickup mode assigned to a still picture and a movie, respectively. A second selecting circuit selects either one of a first focus range advantageous for normal-range pickup and a second focus range assigned to a subject positioned in a range shorter than the first focus range. A controller causes, in the first pickup mode, the focus control mechanism to operate in the focus range selected by the second selecting circuit or causes, in the second pickup mode, the above mechanism to operate in a range including the first focus range without regard to the focus range selected by the second selecting circuit. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which:  
         [0009]    [0009]FIG. 1 is a schematic block diagram showing a digital camera embodying the present invention;  
         [0010]    [0010]FIG. 2 is a flowchart useful for understanding a specific operation of a photometry and range fining controller included in the circuitry of FIG. 1;  
         [0011]    [0011]FIG. 3 is a top planview showing a specific configuration of the digital camera; and  
         [0012]    [0012]FIG. 4 is a rear view showing the specific configuration of the digital camera. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]    Referring to FIG. 1 of the drawings, a digital camera embodying the present invention is generally designated by the reference numeral  10 . As shown, the digital camera  10  includes an optical lens system  21 , a solid-state image sensor  22 , a signal processor  23 , a buffer memory  24 , a photometry and range finding controller  25 , a timing generator  26 , a recorder  27 , a display  28 , a system controller  31 , and an operation panel  32  interconnected as depicted.  
         [0014]    The digital camera  10  is selectively operable both in a pickup mode including a still picture and a movie modes and in a macro mode, which can be turned on or off, under the control of the system controller  31 . In the illustrative embodiment, when the operator of the camera  10  selects the still picture mode as the pickup mode, a focus scanning range varies in accordance with whether or not the macro mode is turned on, as will be described in detail later with reference to FIG. 2. For example, when the macro mode is selected, a preselected range close to a subject, e.g., a range of from 1 m to 0.2 m is established as the focus scanning range. When the macro mode is not selected, the remaining range, i.e., a range between infinity and one meter in this specific case is established as the focus scanning range.  
         [0015]    On the other hand, when the operator selects the movie mode as the pickup mode, the entire range including both of the two ranges mentioned above, e.g., from infinity to 0.2 m is established as the focus scanning range without regard to whether or not the macro mode is selected.  
         [0016]    The lens system  21  includes a zoom and automatic focus (AF) mechanism and an automatic exposure (AE) mechanism although not shown specifically. These mechanisms are driven by control signals  204  fed from the photometry and range finding controller  25 . It is to be noted that signals are designated by the reference numerals attached to signal lines on which they appear.  
         [0017]    The system controller  31  delivers control signals, which include signals indicative of the pickup and macro modes, to the photometry and ranging finding controller  25 . In response, the photometry and range finding controller  25  selects the focus scanning range assigned to the pickup and macro modes and then drives the lens system  21  with the control signals  204 .  
         [0018]    The solid-state image sensor  22  is implemented as a CCD (Charge Coupled Device) image sensor by way of example. When a light image representative of a scene being pickup is captured by the image sensor  22  through the lens system  21 , the image sensor  22  photoelectrically transduces the incident light to a corresponding electric image signal  202  in response to timing pulses  205  fed from the timing generator  26 . The electric image signal  202  is input to the signal processor  23 . The timing generator  26  produces the timing pulses  205  from a reference operation frequency, not shown, inputted- from the system controller  31 .  
         [0019]    The signal processor  23  executes white balance adjustment, gamma correction, analog-to-digital (A/D) conversion, YC (Luminance and Color difference) conversion and other conventional processing with the image signal  202  inputted from the image sensor  22 . The resulting digital image data  203  are written -to the buffer memory  24 . Further, the signal processor  23  compresses the image data  203  when they should be recorded in the recorder  27  as image data  207  or expands such image data  207  read out from the recorder  27 , as needed. In addition, to allow a picture to appear on the display  28 , the signal processor  23  thins, or reduces, YC data and then analog-converts the thinned YC data. The display  28  displays the image data inputted from the signal processor  23  on an LCD (Liquid Crystal Display)  406  (see FIG. 4) as a picture.  
         [0020]    The recorder  27  includes a data recording medium, not shown, and is capable of recording the image data read out from the buffer memory  24  in the data recording medium or reading out the image data from the data recording medium and causing them to be written to the buffer memory  24 . The data recording medium may be implemented as, e.g., a memory card loaded with a semiconductor memory or a package accommodating a magneto-optical disk or similar rotatable recording body and may be removably mounted to the recorder  27 .  
         [0021]    In the movie mode, the signal processor  23  compresses the electric image signal by use of, e.g., a motion JPEG (Joint Photographic cording Experts Group) system and writes the compressed image data in the recorder  27 . More specifically, the signal processor  23  stores the electric image signal in the buffer memory  24 , processes the image signal read out from the buffer memory  24 , and then continuously writes a still picture data in the data recording medium of the recorder  27  with the processed image signal compressed with the motion JPEG system on a picture-by-picture basis.  
         [0022]    As shown in FIGS. 3 and 4 specifically, the operation panel  32  includes various input and select switches, e.g., a power switch  401 , a shutter release button  402 , a pickup mode switch  403 , a macro button  404  and cursor keys  405 . As shown in FIG. 1, the operation panel  32  sends out an operation signal  215  representative of the operator&#39;s manipulation of the operation panel  32  to the system controller  31 . The pickup mode switch  403 , which may be implemented as a slide switch, allows the operator to select either one the still picture and movie modes.  
         [0023]    The system controller  31  controls the operation of the entire digital camera  10  in response to the operation signal  215  inputted from the operation panel  32 . More specifically, in the illustrative embodiment, the system controller  31  determines whether or not the operator has selected the pickup and macro modes in accordance with the operation signal  215  representative of the states of the pickup mode switch  403  and macro button  404 . Particularly, the system controller  31  feeds the control signal  211  representative of the pickup and macro modes to the photometry and range finding controller  25 .  
         [0024]    In operation, the operator first selects the still picture or movie mode on the pickup mode switch  403  of the operation panel  32  and pushes, if desired, the macro button  404  for selecting the macro mode. Subsequently, when the operator pushes the shutter release button  402 , the system controller  31  delivers, based on the operation signal  215  inputted from the operation panel  32 , the control signals  212 ,  211  and  213  or the reference operation frequency (not shown) to the timing generator  26 , photometry and range finding controller  25 , and signal processor  23 . In response, the timing generator  26  generates timing pulses  205  and  206  asynchronous to the reference operation frequency and feeds the timing pulses  205  and  206  to the image sensor  22  and signal processor  23 , respectively. Further, in response to the operation signal  215  representative of the states of the pickup mode switch  403  and macro button  404 , the system controller  31  determines the states of the pickup and macro modes and feeds the control signal  211  indicative of the above states to the photometry and ranging finding controller  25 .  
         [0025]    [0025]FIG. 2 shows a specific operation at flow of the photometry and range finding controller  25 . As shown, the controller  25  determines whether the pickup mode selected by the operator is the still picture or movie modes (step  301 ). If the pickup mode is the still picture mode, then the controller  25  determines whether or not the macro mode is selected (step  302 ). If the answer of the step  302  is positive (YES) , then the controller  25  selects the focus scanning range of 1 m to 0.2 m (step  303 ). The step  303  is followed by the pickup of a still picture (step  305 ). If the answer of the step  302  is negative (NO) , then the controller  25  selects the focus scanning range of infinity to one meter (step  304 ). The step  304  is also followed by the step  305 .  
         [0026]    If the pickup mode selected by the operator is the movie mode, as determined in the step  301 , then the controller  25  simply selects the focus scanning range of infinity to  0 . 2  m (step  310 ), skipping the step  302 . The step  310  is followed by the pickup of a movie (step  311 ).  
         [0027]    In the steps  305  and  311 , the controller  25  controls the lens system  21  in accordance with the focus scanning range thus selected and the result of range finding received from the lens system  21 , thereby adjusting the focus. The lens system  21  so controlled focuses the image of a subject on the image sensor  22 . The image sensor  22  photoelectrically transduces the image of the subject to the electric image signal  202  under the control of the timing generator  26 , as stated earlier.  
         [0028]    The signal processor  23  executes the previously mentioned processing with the image signal  202  and stores the resulting image signal  203  in the buffer memory  24 . The system controller  31  controls the recorder  27  with a control signal  217  such that the recorder  27  controls the writing or the reading of the image signal between the buffer memory  24  and the data recording medium included in the recorder  27 . At the same time, the system controller  31  controls the display  28  with a control signal  218 . As a result, the image signal stored in the buffer memory  24  is transferred to the display  28  and displayed on the LCD  406 , FIG. 4, in the form of a picture.  
         [0029]    On the other hand, in the movie mode, even when the range between the subject and the camera  10  is short, the focus can be advantageously adjusted in the same manner as during normal-range pickup within the focus scanning range without regard to whether or not the macromode is selected. The operator can therefore continuously pick up a desired scene in the movie mode without caring about the macro mode.  
         [0030]    In the illustrative embodiment, the photometry and range finding controller  25  selects either one of the two focus scanning ranges on the basis of the pickup and macro modes, as stated above. Alternatively, the system controller  31  may be configured to determine the focus scanning range in accordance with the procedure of FIG. 2 and send out the control signal  211  indicative of the focus scanning thus determined to the photometry and range finding controller  25 . This successfully reduces the number of signals constituting the control signals  211 .  
         [0031]    In a specific modification of the illustrative embodiment, the digital camera  10  may be provided with two or more different focusing systems, in which case the photometry and range finding controller  25  may select one of the focusing systems in response to the control signal  211  indicative of the pickup mode. For example, the photometry and range finding controller  25  may select a scanning system in the still picture mode or select a continuous or wobbling control mode in the movie mode. In this case, it is noteworthy that in the movie mode the scanning system is not assigned, and therefore, whether or not the macro mode is selected has no influence on focusing in the movie mode.  
         [0032]    In summary, it will be seen that the present invention provides a digital camera capable of being advantageously focused on a desired subject even during short-range pickup. This advantage is derived from the fact that in a still picture mode a focusing time necessary for short-range pickup is reduced when a macro mode is selected while, in a movie mode, a focusing range is broadened without regard to the macro mode.  
         [0033]    The entire disclosure of Japanese patent application No. 2002-118875 filed on Apr. 22, 2002, including the specification, claims, accompanying drawings and abstract of the disclosure is incorporated herein by reference in its entirety.  
         [0034]    While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.