Abstract:
A camera has a viewfinder that forms a subject image to be observed, a multipoint auto-focus adjuster that focuses the subject image on the basis of multiple focus points defined on the subject image, a superimposer that superimposes an indicator mark on a position of a given focus point, and a focus point luminance detector that detects a luminance of the position. Then, the superimposer superimposes the indicator mark such that a brightness of the indicator mark increases as the luminance of the position increases.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a camera with a viewfinder, such as a SLR type camera with a reflex viewfinder. Especially, it relates to a viewfinder-indication associated with focusing. 
     2. Description of the Related Art 
     In an SLR type camera with a multipoint focusing function, multiple focus points are defined on a subject image observed via a viewfinder, which has a pentagonal roof prism and an eyepiece. In the case of the auto-selection mode, when one focus point (for example, center spot) is in focus, an indicator mark is superimposed on the focus point of the observed image. As for the superimpose indication, illuminators such as LEDs are provided in the viewfinder, and an illuminator corresponding to the selected focus point illuminates light so that the user can view the an indicator mark on the focus point via the viewfinder. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a camera that can superimpose a mark on a subject image so as to be easy to see, regardless of the brightness of the subject. 
     A camera according to the present invention has a viewfinder that forms a subject image to be observed, and a multipoint auto-focus adjuster that focuses the subject image on the basis of multiple focus points defined on the subject image, and a superimposer that superimposes an indicator mark on a position of a given focus point. For example, the superimposer has an illuminator that illuminates light for forming the indicator mark, and a light guide member that guides the light to the multiple focus points in the viewfinder by reflecting the illuminated light. The mark is, for example, represented by illuminating light, and the mark is associated with focusing. For example, in the case of manual-selection mode, the superimposer may superimpose the indicator mark as a mark representing a focus point selected from a multiple focus points, by a user. On the other hand, in the case of the auto-selection mode, the superimposer may select one focus point in focus situation, and superimpose the indicator mark as a mark representing that the selected focus point is in a focused situation. 
     The camera according to the present invention further has a focus point luminance detector that detects a luminance of the position. Then, the superimposer superimposes the indicator mark such that a brightness of the indicator mark increases more as the luminance of the image point increases more. The superimposer may adjust the light-intensity in accordance with the luminance, whereas the superimposer adjusts an illuminating-time in accordance with the luminance, for example, when an LED is used for an illuminator. 
     The focus point luminance detector may use a luminance level detected by a multi-segment meter that measures brightness of a subject on the basis of multiple segments. The multiple segments are defined on the subject image, and the multiple focus points are assigned to the multiple segments. Then, the focus point luminance detector detects the luminance of the position in accordance with the brightness of a corresponding segment. 
     On the other hand, the focus point luminance detector may detect a luminance level by using an AF image sensor for focusing. For example, the camera may have a multipoint auto-focus adjuster that focuses the subject image by using a phase-matching method that detects a defocus-amount by using an image sensor for focusing. In this case, the focus point luminance detector may detect the luminance in accordance with an amount of light directed to a corresponding point on the image sensor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from the description of the preferred embodiment of the invention set fourth below together with the accompanying drawings, in which: 
         FIG. 1  is a block diagram of a digital camera according to a first embodiment; 
         FIG. 2  is a cross section view of the viewfinder; 
         FIG. 3  is a cross section view of the viewfinder; 
         FIG. 4  is a view showing an arrangement of multiple segments for metering and positions of multiple focus points; 
         FIG. 5  is a plan view of the screen  32  seen from the upper side; and 
         FIG. 6  is a view showing a subject image viewed via the eyepiece; 
         FIG. 7  is a view showing a main flowchart of the photograph motion. 
         FIG. 8  is a view showing a subroutine of Step S 107  in  FIG. 7 ; 
         FIG. 9  is a view showing a subroutine of Step S 207  in  FIG. 8 ; 
         FIG. 10  is a view showing a subroutine of Step S 303  in  FIG. 9 ; 
         FIG. 11  is a view showing a flowchart of the brightness setting process according to the second embodiment; and 
         FIG. 12  is a view showing a relationship between the luminance level of the focus point and the integral light-receiving time. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the preferred embodiments of the present invention are described with reference to the attached drawings. 
       FIG. 1  is a block diagram of a digital camera according to a first embodiment. 
     When a main switch S 1  is turned ON by operating a main power button (not shown), the electric power is supplied from a power supply circuit  62  to a system control circuit  17  including a CPU  15 , a ROM  16 , and a RAM 18 , as well as other circuits. The system control circuit  17  controls the camera  10 , and feeds control signals to a viewfinder display  54 , an LCD monitor  56 , a metering controller  58 , an AF controller  60 , a pulse generator  64 , a strobe circuit  66 , and so on. 
     When a metering switch S 2  is turned ON by depressing a release button (not shown) halfway, the brightness of a subject is detected by the metering controller  58 . Herein, a multi-segment metering method is performed. Exposure values such as a shutter speed and F number, are calculated on the basis of the brightness. Also, the exposure values are displayed on the viewfinder display  54 , which is viewed below the subject image, by illuminating a viewfinder LEDs  52 , so that the user can confirm the exposure values while viewing the subject image via a viewfinder (herein, not shown). 
     The AF controller  60  detects whether the subject image is in focus by detecting a defocus-amount obtained from the light received on an AF image sensor  61  for focusing. A focusing lens in a photographing optical system  51  is shifted by the AF motor  53  on the basis of the detected defocus-amount. Multipoint auto-focus adjustment can be performed, wherein multiple focus points are defined on the subject image to be viewed via the viewfinder. The user can select a manual-selection mode where the user selects one focus point, or an auto-selection mode that automatically sets a focus point, by operating a cross button (not shown). 
     When a release switch S 3  is turned ON by depressing the release button fully, the photograph motion is performed. The shutter opens and closes so that the subject image is formed on a CCD  57 . Then, image-pixel signals corresponding to the subject image are read from the CCD  57  by the CCD driver  59 , and the image-pixel signals are subjected to various processes to produce image-data. The image data is compressed in the system control circuit  17  and is recorded in a memory card  68 . When a playback mode is selected by operating a mode dial (not shown), a switch in a group of switches  34  is turned ON, and the recorded image is displayed on the LCD monitor  56 . 
     A light source  25  has eleven LEDs  25 L 1 ,  25 L 2 , . . . , and  25 L 11 , which respectively superimpose eleven focus-points on the subject image. Electric current is fed to a given LED, thus the corresponding LED emits light. 
       FIGS. 2 and 3  are cross section views of the viewfinder. 
     A quick return mirror  13  is provided in a mirror box  11 , which is formed backward of the photographing optical system  51 , and is pivotable around a pin  14 . The viewfinder  20  for an SLR type camera is provided upward of the mirror box  11 , and has a pentagonal roof prism  21 , a focusing glass  31 , a field lens (not shown), a screen for superimposing  32 , and an eyepiece  23 . Note, the eyepiece is not shown in  FIG. 3 . The screen  32  is arranged apart from the focusing glass  31  by a given distance and is inclined to the focusing glass  31 . The focusing glass  31  and the screen  32  are supported by a supporting frame  33 . A light detector  24  for metering is provided adjacent to a generally triangular-like exit portion  22  of the pentagonal roof prism  21 . 
     Light “B”, passing through the photographing optical system  51  and reflected on the quick return mirror  13 , passes through the focusing glass  31  and the screen  32 . The pentagonal roof prism  21  has a pair of roof reflecting surfaces  41  and a front reflecting surface  42 , and the light “B” is reflected on the pair of roof reflecting surfaces  41  and the front reflecting surface  42  in order. The light “B” reflected on the front reflecting surface  42  passes through the exit portion  22  and enters into the eyepiece  23 . Thus, a subject image formed on the focusing glass  31  is viewed via the eyepiece  23 . Also, the light “B” enters into the light detector  24  so that the brightness of the subject is detected. 
     As shown in  FIG. 3 , the light source  25 , an illuminating prism  26  is provided backward of the exit portion  22  so as not to interfere with the light-path for the light detector  24 . One LED among the eleven LEDs  25 L 1  to  25 L 11 , constructing the light source  25 , emits illuminating light “C”, which enters into the illuminating prism  26  and is directed to the front reflecting surface  42 . Then, the illuminating light “C” is reflected on the front reflecting surface  42  and the pair of the roof reflecting surfaces  41  in order. The illuminating light “C” reflected on the pair of the roof reflecting surfaces  41  reaches a given position on the screen  32 . 
       FIG. 4  is a view showing an arrangement of multiple segments for metering and positions of multiple focus points.  FIG. 5  is a plan view of the screen  32  seen from the upper side.  FIG. 6  is a view showing a subject image viewed via the eyepiece  23 . 
     As shown in  FIG. 4 , fifteen segments M 1  to M 15  are defined on the subject image viewed via the eyepiece  23 , namely, the fifteen segments M 1  to M 15  are defined on the focusing glass  31 . The luminance of each segment is detected by the light detector  24 . On the other hand, eleven focus points F 1  to F 11  are defined on the subject image so as to match the positions of the focus points F 1  to F 11  with the positions of the segments M 1  to M 11 . Note, a cross mark indicating the focus point and a boundary line of each segment, shown in  FIGS. 4 to 6 , given only for explanation, and are actually invisible. 
     As shown in  FIG. 5 , eleven micro prisms MP 1  to MP 11  are formed on the screen  32  in accordance with the defined positions of the eleven focus points F 1  to F 11 . For example, the micro prism MP 2  is formed at a position corresponding to the focus point F 2 . The eleven LEDs  25 L 1  to  25 L 11  respectively emit light toward the micro prisms MP 1  to MP 11 . The cross section of each micro prism is wave-like, and each micro prism reflects light emitted from a corresponding LED to direct the light to the eyepiece  23 . 
     When an LED corresponding to a given focus point, which is in focus, is illuminated toward a corresponding micro prism, a focus mark “AM”, which is a light-indicator, is viewed on the position of the corresponding focus point by the reflection of light, as shown in  FIG. 6 . The focus mark “AM” is superimposed in red on the subject image viewed via the eyepiece  23 . In  FIG. 6 , the focus mark “AM” is superimposed on the focus point F 2  by illuminating the LED  25 L 2 . 
       FIG. 7  is a view showing a main flowchart of the photograph motion. The process starts when the main power source is turned ON. 
     In Step S 101 , the initial setting is performed for the CPU  15 , and so on. In Step S 102 , it is determined whether the electric power is turned OFF by the user&#39;s operation. When it is determined that the electric power is turned OFF, the process goes to Step S 103 , the power-OFF process is performed. On the other hand, when it is determined that the electric power is not turned OFF, the process goes to Step S 104 . 
     In Step S 104 , a switch process according to the operation to the mode dial or the cross button is performed. In Step S 105 , a display process for the LCD monitor  56  is performed. In Step S 106 , it is determined whether the metering switch S 2  is turned ON by depressing the release button halfway. When it is determined that the metering switch S 2  is not turned ON, the process returns to Step S 102 . On the other hand, when it is determined that the metering switch S 2  is turned ON, the process goes to Step S 107 , wherein the photograph motion process is performed. 
       FIG. 8  is a view showing a subroutine of Step S 107  in  FIG. 7 . 
     In Step S 201 , the counting of time is started to measure a loop-interval. In Step S 202 , a switch process is performed. 
     In Step S 203 , it is determined whether the metering is impossible due to any reason such as an open of a memory card cover, etc. When it is determined that the metering is impossible, the process is terminated. On the other hand, when it is determined that the metering is possible, the process goes to Step S 204 . 
     In Step S 204 , the brightness of the subject detected by the light detector  24 . Herein, the luminance level of the subject image is represented by 256 scales (0 to 255). In Step S 205 , the exposure vales, such as shutter speed and F number, are calculated. In Step S 206 , a display process for indicating the exposure values on the viewfinder display  54  is performed by illuminating the viewfinder LEDs  52 . After step S 206  is performed, the process goes to Step S 207 , wherein the auto-focus adjustment process is performed. 
       FIG. 9  is a view showing a subroutine of Step S 207  in  FIG. 8 . 
     In Step S 301 , it is determined whether the metering switch S 2  is ON. When it is determined that the metering switch S 2  is not ON, the process is terminated. On the other hand, when it is determined that the metering switch S 2  is ON, the process goes to Step S 302 , wherein it is determined whether the auto-selection mode is set by the user. When it is determined that the auto-selection mode is set, the process skips to Step S 305 . On the other hand, when it is determined that the auto-selection mode is not set, namely, the manual-selection mode is set, the process goes to Step S 303 , wherein a brightness setting process is performed. 
       FIG. 10  is a view showing a subroutine of Step S 303  in  FIG. 9 . 
     In Step S 401 , it is determined whether the focus point F 1  corresponding to the metering segment M 1  is selected as an AF adjustment point by the operation to the cross button. When it is determined that the focus point F 1  corresponding to the metering segment M 1  is selected, the process goes to Step S 402 , wherein a luminance level of the segment M 1  is detected by the light detector  24  as a luminance level of the focus point F 1 , and the luminance signal is fed to the system control circuit  17 . Herein, an average luminance level of the segment is detected. On the other hand, when it is determined that the focus point F 1  corresponding to the metering segment M 1  is not selected, the process goes to Step S 403 . 
     Similarly, in Step S 403  to S 421 , it is determined whether the focus points F 2 , F 3 , . . . , and F 11  are selected, and the luminance level of corresponding segment is detected. 
     In Step S 423 , the light-intensity of the LED to be illuminated, namely, the brightness of the focus mark AM to be superimposed is calculated in accordance with the detected luminance level of the segment. A voltage supplied to the LED is determined such that the light-intensity becomes larger as the luminance level of the corresponding segment becomes larger. In other words, the voltage becomes smaller as the detected luminance level becomes smaller. 
     In this embodiment, the electric current of the diode, namely, the light-intensity is calculated in accordance with the following formula.
 
 y=kx+b   (1)
 
Note, the luminance level of the focus mark AM to be superimposed is represented by “y”, the luminance level of the segment corresponding to the position of the focus mark AM to be superimposed is represented by “x”, “k” is a constant, and “b” is an offset value. A corresponding relationship between the light-intensity and the value of electric current supplied to the LED element is stored in the ROM  16  in advance, and the value of the electric current is calculated on the basis of the value of “y”. The value of the electric current is in proportion to the luminance level.
 
     In Step S 424 , it is confirmed that the calculated value of the electric current is in a given range from a minimum limited value to a maximum limited value. When the value of electric current is out of the range, the value of the electric current is set to the maximum or minimum limited value. After Step S 424  is performed, the process goes to Step S 304  in  FIG. 9 . 
     In Step S 304 , the LED corresponding to the selected focus point is illuminated in accordance with brightness of the focus mark AM determined in Step S 303  (S 401  to S 423 ). Namely, the focus mark AM is superimposed on the position of the selected focus point so that the focus mark AM is viewed via the eyepiece  23 . In this case, the focus mark AM is superimposed as a mark that represents a selected focus point, which is different from the auto-selection mode, as described later. 
     In Step S 305 , the defocus-amount is detected on the basis of the signal output from the AF image sensor  61 . Herein, the phase-difference or phase matching method is performed to detect the defocus-amount of the multiple focus points. In Step S 306 , it is determined whether the defocus-amount is in the depth of field, namely, the subject image is in focus. In the case of the manual-selection mode, the defocus-amount corresponding to the selected focus point is detected. In the case of the auto-selection mode, the defocus-amount is detected for each focus point. 
     When it is determined that the defocus-amount is not in the depth of field in Step S 306 , the process goes to Step S 307 , wherein the number of pulses for driving a stepping motor (not shown), which shifts the lens, is calculated in accordance with the defocus-amount. Note that, in the case of auto-selection mode, the focus adjustment is performed for the predetermined primary focus point. In Step S 308 , the lens is driven by a calculated-amount. 
     On the other hand, when it is determined that the defocus-amount of the selected focus point or at least one focus point is in the depth of field in Step S 306 , the process goes to Step S 309 , wherein one focus point, namely, the selected focus point, one focus point in focus, or one focus point among plural focus points in focus, is set or selected to superimpose the focus mark AM. Herein, a center focus point “F 6 ” is primarily set in the auto-selection mode. 
     In Step S 310 , similarly to Step S 303 , the brightness of the focus mark “AM” is set, namely, the electric current is calculated. Then, in Step S 311 , the focus mark AM is superimposed in red on the corresponding focus point. In this case, the focus mark AM is superimposed as a mark that represents a focus of the selected focus point. After Step S 311  is performed, the process goes to Step S 208  in  FIG. 8 . 
     In  FIG. 8 , it is determined whether the release switch S 3  is turned ON by fully depressing the release button. When it is determined that the release switch S 3  is not turned ON, the process skips to Step S 210 . On the other hand, when it is determined that the release switch S 3  is turned ON, the process goes to Step S 209 , wherein the photograph motion is performed so that the subject image is recorded. 
     In Step S 210 , the time is counted from when the subroutine starts. 
     In Step S 211 , it is determined whether the time has passed the loop-interval, which is, for example, a multiple of 128 (ms). When it is determined that the time has not passed the loop-interval, the process returns to Step S 202 . On the other hand, when it is determined that the time has passed the loop-interval, the photograph motion process is terminated. The main routine of Step S 102  to S 107  shown in  FIG. 4  is repeatedly performed until the main power is turned OFF. 
     With reference to  FIGS. 11 and 12 , a camera according to a second embodiment is explained. The second embodiment is different from the first embodiment in that the luminance level of the focus point is detected in accordance with light that reaches the AF image sensor  61  for focusing. Further, the brightness of the focus mark is adjusted by a lighting-time. Other constructions are the same as those of the first embodiment. 
       FIG. 11  is a view showing a flowchart of the brightness setting process according to the second embodiment, which is performed as a subroutine of Step S 310 .  FIG. 12  is a view showing a relationship between the luminance level of the focus point and the integral light-receiving time of the AF image sensor  61 . 
     In Step S 501 , the integral light-receiving time of the image sensor  61  is detected, and the luminance level is calculated. Note that, the integral light-receiving time is detected for the position corresponding to the focus point selected in Step S 309 . 
     As shown in  FIG. 12 , as for the AF image sensor  61 , the integral total light-receiving time becomes shorter as the luminance level of the light, which reaches the image sensor  61 , becomes greater. Note that, the luminance level is herein represented by voltage (EV). The brightness of the selected focus point is determined in accordance with the total light-receiving time. 
     In Step S 502 , an illuminating-time of the LED is calculated in accordance with the detected luminance level. Each LED emits light in pulses, therefore, the brightness of the focus mark AM becomes greater as the lighting-time becomes greater. In Step S 503 , similarly to Step S 424 , the calculated electric current is confirmed. Then, similarly to the first embodiment, the focus mark AM is superimposed as shown in Step S 311  in  FIG. 9 . The luminance level of the focus point may be detected regardless of the multiple segments M 1  to M 16  for metering. 
     Finally, it will be understood by those skilled in the art that the foregoing description is of preferred embodiments of the device, and that various changes and modifications may be made to the present invention without departing from the spirit and scope thereof. 
     The present disclosure relates to subject matters contained in Japanese Patent Application No. 2004-184789 (filed on Jun. 23, 2004), which is expressly incorporated herein, by reference, in its entirety.