Abstract:
An image sensing apparatus invention has an image sensing device for sensing a subject image from a range which is wider than a photographic range, a processor for calculating position information of a subject with respect to the photographic range based on an output from the image sensing device, a discriminator for determining whether photographing is appropriately performed or not, based on information calculated by the processor, and a notifier for notifying a result of determination by the discriminator before photographing. In this structure, appropriate photographing can be performed by referring to the notifying contents of the notifier.

Description:
This application is based on application No. H10-160282 filed in Japan, the contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an image sensing apparatus for sensing a subject image. 
     2. Description of the Prior Art 
     When taking a picture with a camera, the photographer performs framing before releasing the shutter. Framing is important because the quality of the taken picture largely depends on whether framing is appropriately made or not. 
     At a normal photographing distance, since the area within the finder field frame is always taken on the film, the photographic range is decided with reference to the finder field frame. In short-range photographing, the photographic range is decided with reference to a parallax correction frame provided in the finder. The parallax correction frame is provided for correcting the parallax amount which increases in short-range photographing. In addition to such a camera, a camera is known which is, although high in cost, structured so that the parallax correction frame moves in accordance with the distance measurement result. In this camera, the photographic range is decided with reference to the correction frame that moves. 
     It is also important in framing to set a composition where the subject is not backlighted. However, more and more cameras have recently been designed so as to compensate for exposure by detecting that the subject is backlighted. Therefore, it has become unnecessary for the photographer to be aware of the position of the sun. 
     As a cause of failure in releasing the shutter, camera shake is considered. Cameras embodying various ideas to prevent camera shake have previously been known. For example, there is a camera having a function of compensating for camera shake by moving the optical system in accordance with the camera shake amount. According to such a camera, failures caused by camera shake can be reduced although this camera is large in size and high is cost. 
     However, even in cameras embodying various ideas as described above, taken pictures can be failures. The following are examples of causes of such failures: A beginner sometimes takes pictures without noticing that a part of the subject is situated outside the field frame. In the case of a single-lens reflex camera, although no parallax is caused, there are cases where the photographer does not notice that a part of the subject is situated outside because his or her attention is caught by other operations. 
     When photographing is performed in a macro mode with a camera having a macro mode capable of short-range photographing at a photographing distance of 40 to 50 cm, although the camera has a parallax correction frame for the macro mode, there are cases where the photographer forgets the presence of the correction frame during photographing and an upper part of the subject (in the case of photographing in landscape orientation) is situated outside. With respect to the lower part of the subject, although even a part not seen in the finder is included in the photographic range, there is no means for confirming it and the photographer cannot help but depend on experience. Consequently, there are cases where the photographer cannot set a composition which he or she desires. 
     Even if a camera shake compensating function is provided, since this function is limited, the taken pictures can be blurred according to photographing conditions. For example, when a child is photographed, if the child moves when the shutter is released, the taken picture is a failure according to the shutter speed. Further, zoom lens systems have recently become the norm, and particularly, on the telephoto side in compact cameras, the F number of the lens increases and the shutter speed is controlled so as to increase the exposure time, so that the possibility that the taken picture is blurred is high. 
     Moreover, the backlight correction is also limited. Correction cannot be made when a bright point light source is present within the photographic range and when a light source is situated outside in the vicinity of the finder field, so that there are cases that flare is caused in the taken picture. In the case of compact cameras, since the taking lens and the finder optical system are different, it is difficult to grasp how much the influence of backlight is, so that there are cases where the taken picture is a failure. Since whether the taken picture is failure or not cannot be found until the picture is developed and printed, it is impossible to photograph the subject again on the spot. 
     SUMMARY OF THE INVENTION 
     In view of the above-mentioned problem, an object of the present invention is to provide an image sensing apparatus in which failures in framing are reduced, further, an image sensing apparatus in which when failing in photographing, the photographer notices the failure immediately after the photographing. 
     To achieve the above-mentioned object, an image sensing apparatus of the present invention has an image sensing device for sensing a subject image from a range being wider than a photographic range, a processor for calculating position information of a subject with respect to the photographic range based on an output from the image sensing device, a discriminator for determining whether photographing is appropriately performed or not, based on information calculated by the processor, and a notifier for notifying a result of determination by the discriminator before photographing. 
     Moreover, an image sensing apparatus of the present invention has a taking lens, a finder optical system having an optical axis being different from that of the taking lens, an image sensing device for sensing a subject image, a processor for calculating information on parallax based on an output from the image sensing device, a discriminator for determining whether photographing is appropriately performed or not, based on information calculated by the processor, and a notifier for notifying a result of determination by the discriminator before photographing. 
     Moreover, an image sensing apparatus of the present invention has an image sensing device for sensing a subject image, a detector for detecting a subject distance based on an output from the image sensing device, a processor for calculating position information of a subject based on a result of detection by the detector, a discriminator for determining whether photographing is appropriately performed or not, based on information calculated by the processor, and a notifier for notifying a result of determination by the discriminator before photographing. 
     Moreover, an image sensing apparatus of the present invention has an image sensing device for sensing a subject image, a memory for storing therein image data before photographing and image data after photographing by the image sensing device, a comparator for comparing the image data before photographing and the image data after photographing stored in the memory, a discriminator for determining whether photographing was appropriately performed or not, based on a result of comparison by the comparator, and a notifier for notifying a result of determination of the discriminator after photographing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     This and other objects and features of this invention will become clear from the following description, taken in conjunction with the preferred embodiments with reference to the accompanying drawings in which: 
     FIG. 1 is a block diagram schematically showing the structure of a camera of this embodiment; 
     FIG. 2 is a schematic view of a pair of area sensors; 
     FIG. 3 is a view showing the field of view in the finder; 
     FIG. 4 is a view showing the relationship among a field frame, a photographic range and an area sensor range in a first embodiment; 
     FIG. 5 is a view showing a manner of range display in the first embodiment; 
     FIG. 6 is a view showing a manner of warning that the subject is too large in the first embodiment; 
     FIG. 7 is a view showing a manner of warning that a part of the subject is situated outside in the first embodiment; 
     FIG. 8 is a view showing a condition where framing is appropriately made in the first embodiment; 
     FIGS. 9 a-b  are views showing a manner of warning that flare is caused in the first embodiment; 
     FIGS. 10 a-c  are views showing a manner of warning that blur is caused in the first embodiment; 
     FIG. 11 is a view showing an exterior of a camera in a second embodiment; 
     FIGS. 12 a-b  are views showing a manner of warning that an upper part of the subject is situated outside in the second embodiment; 
     FIGS. 13 a-b  are views showing a manner of warning that a lower part of the subject is situated outside in the second embodiment; 
     FIG. 14 is a view showing a condition of a subject for explaining framing determination; 
     FIG. 15 is a view showing the distance distribution data of each pixel of the area sensor for explaining the framing determination; and 
     FIG. 16 is a block diagram of a camera of the first embodiment. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a block diagram briefly showing the structure of an image sensing apparatus according to an embodiment of the present invention. The image sensing apparatus of this embodiment is a camera. When the shutter button is depressed, light incident through a taking lens  1  is recorded onto the film by a non-illustrated image forming portion (photographing). The subject can be viewed through a finder  2 . The viewer performs framing while looking through a sight window provided in the finder  2 . A photometric portion  3  detects the quantity of the incident light from the subject by a light receiving device. 
     A distance measurement portion  4  comprising a pair of area sensors described later splits the light incident from the direction of the subject into two parts and images each part of the light onto the corresponding area sensor. The pair of area sensors convert the received image into electric signals. The distance measurement portion  4  calculates the distance measurement data based on the electric signals. 
     An area sensor  28  receives the light incident from the direction of the subject and converts the received image into electric signals. When a sufficient range of image including the photographic range can be received by the area sensors of the distance measurement portion  4 , it is unnecessary to provide the area sensor  28  in addition to the area sensors. When the area sensor  28  is provided, since it is necessary for the distance measurement portion  4  to be capable of calculating only distance measurement data, a pair of line sensors may be provided instead of the pair of area sensors. 
     A photometric information calculating portion  5  calculates appropriate aperture value and shutter speed based on the result of the detection by the photometric portion  3 . While the photometric portion  3  and the distance measurement portion  4  are separately provided in this embodiment, the distance measurement portion  4  may be used also as the photometric portion. In this case, the photometric information calculating portion  5  calculates the data based on the result of the detection by the distance measurement portion  4 . 
     A distance measurement information calculating portion  6  calculates an appropriate position of the taking lens  1  based on the distance measurement data of the distance measurement portion  4 . A taking lens control portion  12  controls the position of the taking lens and the aperture value and the shutter speed at the time of photographing based on the data calculated by the photometric information calculating portion  5  and the distance measurement information calculating portion  6  to perform automatic focus detection and automatic exposure compensation. 
     An image processing portion  8  first captures image data obtained by the distance measurement portion  4  or the area sensor  28 . Then, based on the image data, when the shutter button is depressed under the condition at that time, the image processing portion  8  determines whether the size and the position of the subject in the actual image plane (photographic range) are appropriate or not (framing determination) and whether there is a possibility that flare is caused in the taking optical system or not (flare determination). When the size and the position are not appropriate and when there is a possibility that flare is caused, data to notify the photographer of that are transmitted to a display control portion  10 . The captured image data are transmitted to a memory portion  9  and stored therein. 
     After photographing is finished, the image processing portion  8  compares the image data when the shutter is open and the image data when the shutter is closed based on the data stored in the memory portion  9 , and determines whether or not the taken image is blurred by a predetermined amount or more (blur determination). When it is determined that the taken image is blurred, data to notify the photographer of that are transmitted to the display control portion  10 . 
     The photometric information calculating portion  5 , the distance measurement information calculating portion  6 , the image processing portion  8 , the taking lens control portion  12 , the display control portion  10  and the memory portion  9  are formed in a CPU  11  in the camera. The data calculated by these portions or the data necessary for the calculation are all stored in the memory portion  9 . These portions read out necessary data from the memory portion  9  whenever necessary. 
     Based on the transmitted data, the display control portion  10  controls the display of a display portion  7  in the finder  2 . 
     FIG. 2 is a view schematically showing the area sensors of the distance measurement portion  4 . The distance measurement portion  4  has a pair of left and right area sensors  40 . The light incident on the distance measurement portion  4  is split into two parts and applied to the area sensors. At each area sensor, the incident light is converted into electric signals. The distance measurement data are calculated by the phase difference detection method based on the electric signals obtained by the two area sensors  40 . When the area sensor  28  is not provided, the image data obtained by at least one of the two area sensors  40  are transmitted to the image processing portion  8 . 
     It is assumed that the detection range of the image detected by the area sensors  40  or the area sensor  28  includes or substantially includes the photographic range of the image taken by the taking lens  1 , and is larger than the photographic range. 
     FIG. 3 is a view schematically showing the field of view through a sight window  2   b  of the finder  2 . The finder  2  has a field frame  2   a  showing the range of the actual image plane. The field frame  2   a  comprises a light image frame. In order that everything seen in the field frame  2   a  is taken onto the film, the field frame  2   a  is smaller than the actual image plane. 
     Reference numeral  71  represents a liquid crystal display portion disposed below the field frame  2   a . When it is determined in the flare determination that there is a possibility that flare is caused, a flare mark  71   a  is displayed. When it is determined in the blur determination that the taken image is blurred by the predetermined amount or more, a blur mark  71   b  is displayed. Reference numeral  70  represents a framing determination display portion disposed in the field frame  2   a . The display portion  70  comprises a plurality of line-form indicators such as an upper central indicator  70   a , a central indicator  70   b  and a lower central indicator  70   c . These indicators are blinked or lit up. 
     The framing determination display portion  70  may have any configuration as long as a line-form image is viewed by the viewer at the time of display. For example, the framing determination display portion  70  may have a configuration such that a transmissive LCD is disposed in the same position as the light image frame of the field frame  2   a . In this configuration, by controlling the LCD so as to be switched between the transmitted condition and the un-transmitted condition, a line-form image in the display portion  70  is viewed or is not viewed in the viewer&#39;s field of view. It is assumed that the condition where the image is viewed is the displayed condition. The display portion  7  comprises the LCD display portion  71  and the framing determination display portion  70 . 
     Hereinafter, the framing determination, the flare determination and the blur determination, and the display controls based on the results of these determinations will concretely be described with reference to the drawings. Of the camera of FIG. 1, a camera in which the optical system of the taking lens  1  and the optical system of the distance measurement portion  4  are the same like a single-lens reflex camera will be referred to as a camera of the first embodiment, and a camera in which the optical systems are different will be referred to as a camera of the second embodiment. Both of these cameras will be described. 
     First, an example of the camera of the first embodiment will be shown. FIG. 16 is a block diagram of a single-lens reflex camera according to this embodiment. A taking lens portion  27  is attached to the front surface of a camera body  26 . The taking lens  1  is disposed on the optical axis  29 . In the rear of the taking lens  1 , a main mirror  23  is disposed so as to face upward at 45 degrees. In the rear of the main mirror  23 , a film exposure plane  25  is disposed. At least a part of the main mirror  23  is a half mirror. 
     Between the half mirror part of the main mirror  23  and the film exposure plane  25 , a sub mirror  24  whose rotation axis is attached to the rear surface of the main mirror  23  is disposed so as to face downward at 45 degrees. The sub mirror  24  reflects the distance measurement luminous flux transmitted by the half mirror part of the main mirror  23 , and directs it to the distance measurement portion  4  disposed below the mirror box of the camera body. 
     At the time of photographing, the main mirror  23  and the sub mirror  24  are rotated upward so as to retreat from the optical axis  29 , and the photographing luminous flux having passed through the taking lens  1  is imaged on the film exposure plane  25 . Reference numeral  30  represents the shutter. 
     A focusing screen  18  and a pentagonal roof prism  17  are formed above the main mirror  23 . The light reflected upward at the main mirror  23  is imaged on the focusing screen  18 . The user of the camera can view the image on the focusing screen  18  through the pentagonal roof prism  17 . In the camera of this embodiment, the light having passed through the pentagonal roof prism  17  is also supplied to the area sensor  28 . Therefore, in this embodiment, the image data formed by the area sensor  28  in FIG. 1 are transmitted to the image processing portion  8 , and the image processing portion  8  performs various processes by use of the data. 
     An auxiliary light emitting portion  15  emits light when distance measurement is impossible because of low subject brightness and low contrast based on an instruction from the CPU  11 . A light adjusting module  22  adjusts the light emission amount of a non-illustrated flash portion. 
     In a lens CPU  16 , lens information is stored. Of the information, information necessary for automatic focus detection control and automatic exposure compensation is supplied to the CPU  11 . An instruction from the lens control portion  12  (see FIG. 1) of the CPU  11  is transmitted to an AF actuator  20  which drives the motor for driving the taking lens  1 . An AF encoder  21  converts the number of revolutions of the motor into a signal in order to control the number of revolutions. This signal is transmitted to the CPU  11 . Monitoring this signal, the CPU  11  controls the number of revolutions of the AF motor. 
     The revolution of the AF motor is transmitted from the body side  26  to the lens side  27  by a lens driving system  19 , and the lens  1  is driven to complete focusing. The structure other than this will not be described because it has been described with reference to FIG.  1 . 
     FIG. 4 shows the relationship among the field frame  2   a , the photographic range (actual image plane)  1   a  and the area sensor range  28   a  (image detection range of the area sensor  28 ). As mentioned previously, the field frame  2   a  is smaller than the photographic range  1   a.    
     Immediately after the photographer looks through the finder  2 , the upper central indicator  70   a  and the lower central indicator  70   c  light up as shown in FIG. 5 so that the photographer clearly recognizes the field frame  2   a . The field frame  2   a  which is viewed as a light image frame can be recognized by a careful view. However, the field frame  2   a  is difficult to recognize in some light conditions because it is a thin line. By lighting the indicators  70   a  and  70   c , the viewer can clearly recognize the field frame  2   a.    
     When it is determined in the framing determination that the subject is too large to fall within the photographic range  1   a , the upper central indicator  70   a  and the lower central indicator  70   c  are blinked as shown in FIG. 6 to thereby warn the photographer that the subject is too large. Warning is also provided when there is a problem with the position of the subject although there is no problem with the size of the subject. For example, when an upper part of the subject is situated outside the photographic range  1   a , the upper central indicator  70   a  is blinked as shown in FIG. 7 to thereby warn the photographer that the upper part is situated outside. 
     Since the field frame  2   a  is smaller than the photographic range  1   a , when a part of the subject is situated outside the field frame  2   a , it is difficult to determine whether the subject is included in the photographic range  1   a  or not. By providing the warnings as described above, the photographer can easily perform framing and failures due to framing such that a part of the subject is situated outside can be prevented. 
     In any of the displays, the indicator is turned off when framing is made so that the subject is of an appropriate size and situated in an appropriate position as shown in FIG.  8 . 
     FIG. 9 shows an example for explaining the flare determination and the display control based on the flare determination in the camera of the first embodiment. When a high-brightness light source such as the sun is detected in the area sensor range  28   a  as shown in (a) of FIG. 9, it is determined in the flare determination that the possibility that flare is caused in the taking optical system is high since a high-brightness light source is situated in the vicinity of or inside the photographic view angle. By the display control based on the determination result, the flare mark  71   a  is displayed in the liquid crystal display portion  71  as shown in (b) of FIG.  9 . In response to the warning, the photographer can set a more appropriate photographic range by performing framing again. 
     In the flare determination, the structure such that the area sensor range  28   a  is larger than the photographic range  1   a  like in this embodiment is particularly effective. With this structure, even when a high-brightness light source is situated in the vicinity of the photographic view angle as shown in (a) of FIG. 9, the light source can be detected. 
     FIG. 10 shows an example for explaining the blur determination and the display control based on the blur determination in the camera of the first embodiment. To perform the blur determination, the position of a subject image  14   a  obtained from the image data of the area sensor  28  when the shutter is open (a) is compared with the position of a subject image  14   b  obtained from the image data of the area sensor  28  when the shutter is closed (b), and it is determined whether or not the shift amount  14   c  between the two images  14   a  and  14   b  is a predetermined value or larger. When the shift amount  14   c  is the predetermined value or larger, it is determined that blur is caused. By the display control based on the determination result, the blur mark  71   b  is displayed in the liquid crystal display portion  71  as shown in (c). 
     This warning is very effective since the photographer can photograph the subject again in response to the warning. If the warning that blur is caused is not provided, it is only after the picture is developed and printed that the photographer finds that blur occurred, and at that time, it is impossible for the photographer to photograph the subject again. 
     Subsequently, an example of the camera of the second embodiment will be described. FIG. 11 briefly shows an exterior of the camera of the second embodiment. On the taking lens  1 , the distance measurement portion  4  and the finder  2 , light is incident through different optical systems. In addition, a flash  13  is formed. In the camera of this embodiment, the area sensor  28  in the block diagram of FIG. 1 is not provided. Therefore, in the image processing portion  8 , processing is performed based on the image data detected by the area sensors  40  of the distance measurement portion  4 . 
     (a) of FIG. 12 shows an example of the relationship among the field frame  2   a , the photographic range  1   a  and the area sensor range  40   a  (image detection range of the area sensors  40 ) in the camera shown in FIG.  11 . Since light is incident on the taking lens  1 , the distance measurement portion  4  and the finder  2  through different optical systems in the camera of this embodiment, the centers of the area sensor range  40   a , the field frame  2   a  and the photographic range  1   a  do not coincide. In the field frame  2   a  and the photographic range  1   a , a parallax which differs according to the subject distance is caused. 
     When a subject being a short distance away is photographed, if framing is performed without consideration of parallax, it can happen that the subject does not fall within the photographic range  1   a  although being situated within the field frame  2   a  as shown in (a) of FIG.  12 . In this case, it is determined in the framing determination that an upper part is situated outside. By the display control based on the determination result, the central indicator  70   b  coinciding with the upper limit of the photographic range  1   a  is blinked as shown in (b) of FIG.  12 . 
     Moreover, it can happen that although parallax is considered, the prediction of the parallax amount is erroneous and a lower part is situated outside the photographic range  1   a  as shown in (a) of FIG.  13 . In this case, it is determined in the framing determination that a lower part is situated outside. By the display control based on the determination result, the lower central indicator  70   c  is blinked. 
     By the above-described control, failure of framing can be prevented even when there is a large parallax. When a subject not being a short distance away is photographed, a warning is provided in a similar manner. The flare warning and the blur detection display are provided like in the first embodiment. 
     While examples of control in the first and the second embodiments have been shown, it is desirable that various warnings be provided by controlling the indicators of the framing determination display portion  70 . Although it is desirable for the photographer to remember the meanings of the displays, since the contents of warnings and the positions of the displays correspond to each other, the photographer can visually recognize the meanings even if he or she does not remember them. Since the indicator is turned off when an appropriate framing is made, framing is performed by moving the field of view until the indicator is turned off. 
     Subsequently, a detailed processing method of the framing determination will be described with reference to FIGS. 14 and 15. It is assumed that a framing as shown in FIG. 14 is made. The photographic range  1   a  which varies according to the subject distance is not decided until the framing determination is performed. 
     The area sensors  40  or the area sensor  28  comprises a plurality of photoelectrically converting elements each corresponding to a pixel. The distance distribution data of each pixel are obtained by the phase difference detection method based on the image data of the area sensor. FIG. 15 shows the distance distribution data. The numbers in the pixels are distance data. The object configuration is grasped by overlaying the image data on the distance distribution data. In FIG. 15, the object configuration of the main subject is determined to be a configuration as shown by the hatched area  30 . 
     The above-described data are transmitted from the distance measurement portion  4  or the area sensor  28  to the image processing portion  8 . The image processing portion  8  estimates the photographic range  1   a  based on the distance to the main subject, and calculates whether a part of the main subject is situated outside the photographic range  1   a  or not and whether the main subject is of the size that falls within the photographic range  1   a  or not. In this case, since the subject is too large, a warning as shown in FIG. 6 is provided. 
     While in this embodiment, the photographer is provided with information effective in framing, information to notify the photographer of the possibility that flare is caused and information to notify the photographer that blur is caused by the indicators of the display portion  7 , the notifier is not limited to indicators. For example, sounds may be used to provide the photographer with various kinds of information. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.