Abstract:
An image sensing apparatus includes an image sensor; an image display device; a display designating unit that designates whether or not the sensed image is displayed by the image display device; and a focus evaluating value obtaining device that obtains a focus evaluating value for adjusting a focus. The focus evaluating value obtaining device obtains the focus evaluating value based on an image signal that corresponds to a part of a region of an display image displayed by the image display device if the display designating unit does not designate that the sensed image is displayed by the image display device when the image of the subject is sensed by said image sensor.

Description:
FIELD OF THE INVENTION 
   The present invention relates to an image sensing apparatus such as an electronic camera and a control method thereof. 
   BACKGROUND OF THE INVENTION 
   Conventionally, an image sensing apparatus such as an electronic camera is known which records and reproduces a still picture or an moving picture with a recording medium such as a memory card having a solid state memory device as a recording medium. Some type of such an apparatus is provided with not only an optical finder (OVF) but also an electronic finder composed of a color liquid crystal panel or the like. 
   This image sensing apparatus is configured such that an image of a subject is sensed by an image sensing device such as a CCD to obtain an image signal, and processing such as auto-focus (AF) control, automatic exposure (AE) control and auto-white balance (AWB) are performed using the signal. In order to display a favorable moving picture on the electronic finder, it is necessary to supply an image signal in the order of 60 frames per second. In addition, in the case in which a still picture is sensed, it is important not to miss timing for releasing a shutter. For this purpose, the above-mentioned processing such as AF control, AE control and AWB control is required to be performed at a high speed. 
   However, focusing cannot always be attained using an image signal of one frame and an AF control operation is performed using an image signal of a plurality of frames with the above-mentioned conventional image sensing apparatus. Thus, there is a problem in that the AF control processing takes long and, as a result, the interval between the time when a shutter button is pressed and the time when an image of a subject is actually sensed (shutter time lag) tends to be long. 
   SUMMARY OF THE INVENTION 
   The present invention has been achieved in order to solve the above-mentioned problem of the conventional art. It is an object of the present invention, for example, to reduce burdens of focusing processing in sensing an image, which does not require image display, and to shorten the shutter time lag. 
   According to the present invention, there is provided an image sensing apparatus, comprising: 
   an image sensor that senses an image of a subject to obtain an image signal; 
   an image display device that is capable of displaying a sensed image based on said image signal obtained by said image sensor; 
   a display designating unit that designates whether or not said sensed image is displayed by said image display device when the image of the subject is sensed by said image sensor; and 
   a focus evaluating value obtaining device that obtains a focus evaluating value for adjusting a focus based on said image signal obtained by said image sensor, said focus evaluating value obtaining device obtaining said focus evaluating value based on an image signal which is obtained by said image sensor and corresponds to a part of a region of an display image displayed by said image display device, if said display designating unit does not designate that said sensed image is displayed by said image display device when the image of the subject is sensed by said image sensor. 
   According to the present invention, there is also provided a control method of an image sensing apparatus, comprising: 
   an image sensing step that senses an image of a subject to obtain an image signal; 
   an image displaying step that is capable of displaying a sensed image based on said image signal obtained by said image sensing step; 
   a display designating step that designates whether or not said sensed image is displayed by said image displaying step when the image of the subject is sensed by said image sensing step; and 
   a focus evaluating value obtaining step that obtains a focus evaluating value for adjusting a focus based on said image signal obtained by said image sensing step, said focus evaluating value obtaining step obtaining said focus evaluating value based on an image signal which is obtained by said image sensing step and corresponds to a part of a region of an display image displayed by said image displaying step if said display designating step does not designate that said sensed image is displayed by said image displaying step when the image of the subject is sensed by said image sensing step. 
   According to the present invention, there is also provided a storage medium in which a control program of an image sensing apparatus is stored, wherein said control program comprises: 
   a code of an image sensing step that obtains an image signal by sensing an image of a subject; 
   a code of an image displaying step that is capable of displaying a sensed image based on said image signal obtained in said image sensing step; 
   a code of a display designating step that designates whether or not the sensed image is displayed by said image displaying step when an image of the subject is sensed by said image sensing step; and 
   a code of a focus evaluating value obtaining step that obtains a focus evaluating value for adjusting a focus based on said image signal obtained by said image sensing step, said focus evaluating value obtaining step obtaining said focus evaluating value based on an image signal which is obtained by said image sensing step and corresponds to a part of a region of an display image displayed by said image displaying step if said display designating step does not designate that said sensed image is displayed by said image displaying step when the image of the subject is sensed by said image sensing step. 
   According to the present invention, there is also provided an image sensing apparatus, comprising: 
   an image sensor for sensing an image of a subject to output an image signal; 
   a display for displaying a sensed image based on said image signal; 
   a designation unit for designating whether or not said sensed image is displayed by said display when an image is sensed by said image sensor; and 
   a calculation unit for calculating a focus evaluating value for focus adjustment based on said image signal, 
   wherein said calculation unit calculates said focus evaluating value based on a part of said image signal if said designation unit designates not to display said sensed image. 

   
     Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. 
       FIG. 1  is a block diagram showing an example of a configuration of an image sensing apparatus in accordance with an embodiment of the present invention; 
       FIGS. 2 to 5  show a flow chart of image sensing processing in the image sensing apparatus; 
       FIG. 6  illustrates an image sensing area of an image sensing device corresponding to a display screen of one frame of a sensed image; and 
       FIG. 7  illustrates an image sensing area of an image sensing device corresponding to a display screen of one frame of a sensed image. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Preferred embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. 
     FIG. 1  is a block diagram showing a configuration of an image sensing apparatus in accordance with an embodiment of the present invention. This apparatus is configured, for example, as an electronic camera. 
   In the drawing, reference numeral  100  denotes an image processing apparatus (image sensing apparatus), reference numeral  10  denotes a photographing lens consisting of a zoom lens and a focus lens, reference numeral  12  denotes a shutter provided with a focusing function, and reference numeral  14  denotes an image sensing device, which converts an optical image to an electric signal. Reference numeral  16  denotes an A/D converter, which coverts an analog signal output of the image sensing device  14  to a digital signal. Reference numeral  18  denotes a timing generation circuit, which supplies a clock signal and a control signal to the image sensing device  14  and the A/D converter  16  and is controlled by a memory control circuit  22  and a system control circuit  50 . 
   Reference numeral  20  denotes an image processing circuit, which applies predetermined pixel interpolation processing or color conversion processing with respect to data form the A/D converter  16  and data from the memory control circuit  22 . In addition, in the image processing circuit  20 , predetermined operation processing is performed using the sensed image data. In addition, AF (auto focus) processing of the TTL (Through the Lens) method in which the system control circuit  50  applies control with respect to an exposure control section  40  and a distance measurement control section  42  based on a result found by the operation, AE (automatic exposure) processing and EF (flash pre-light emission) processing are performed. Moreover, in the image processing circuit  20 , predetermined operation processing is performed using the sensed image data, and AWB (Auto White Balance) processing of the TTL method based on a result found by the operation is also performed. 
   Reference numeral  22  is a memory control circuit, which controls the A/D converter  16 , the timing generation circuit  18 , the image processing circuit  20 , an image display memory  24 , a D/A converter  26 , a memory  30  and a compression and extension circuit  32 . 
   Data of the A/D converter  16  is written in the image display memory  24  or the memory  30  via the image processing circuit  20  and the memory control circuit  22  or directly through the memory control circuit  22 . 
   Reference numeral  24  denotes the image display memory, reference numeral  26  denotes the D/A converter and reference numeral  28  denotes an image display consisting of a TFT-LCD (thin film transistor-liquid crystal display) or the like. Image data for display written in the image display memory  24  is displayed by the image display  28  via the D/A converter  26 . If sensed image data is sequentially displayed using the image display  28 , it is possible to realize an electronic finder function. In addition, the image display  28  can arbitrarily turn on/off display according to an instruction of the system control circuit  50 , and power consumption of the image processing apparatus  100  can be significantly reduced if display is turned off. 
   Reference numeral  30  denotes the memory for storing photographed still pictures, moving pictures and voice data, and is provided with a storage capacity sufficient for storing a predetermined number of still pictures and a predetermined length of time of moving pictures. Thus, even in the case of continuous photographing for photographing a plurality of still pictures continuously or panoramic photographing, it is possible to write images in the memory  30  at high speed and in large quantity. In addition, the memory  30  can also be used as a work area of the system control circuit  50 . 
   Reference numeral  32  denotes the compression and extension circuit for compressing or extending image data by adoptive discrete cosine conversion (ADCT) or the like. The compression and extension circuit  32  reads an image stored in the memory  30  to apply compression processing or extension processing to it, and then writes the processed data in the memory  30 . 
   Reference numeral  40  denotes the exposure control section, which controls the shutter  12  and has a flash adjustment function by linking with a flash  404 . Reference numeral  42  denotes the distance measurement control section, which controls focusing of the photographing lens  10 . The exposure control section  40  and the distance measurement control section  42  are controlled using the TTL method. The system control circuit  50  controls the exposure control section  40  and the distance measurement control section  42  based on a result of operation found by operating sensed image data by the image processing circuit  20 . 
   Reference numeral  44  denotes a zoom control section, which controls zooming of the photographing lens  10 . Reference numeral  46  denotes a barrier control section, which controls operation of a protective section  102  being a barrier. Reference numeral  48  denotes a connector, which is also called an accessory shoe and is provided with an electric contact with the flash apparatus  400  and a mechanical solid-state device together. 
   Reference numeral  50  denotes the system control circuit, which controls the entire image processing apparatus  100 . Reference numeral  52  denotes a memory, which stores constants, variables, programs or the like for operation of the system control circuit  50 . 
   Reference numeral  54  denotes a display section such as a liquid crystal display device and a speaker, which displays an operational state, a message or the like using characters, images, voices or the like according to execution of a program in the system control circuit  50 . This display section  54  is installed at a single or a plurality of places in the vicinity of an operating section of the image processing apparatus  100  where it can be easily recognized visually. The display section  54  is composed of a combination of, for example, an LCD (liquid crystal display) or an LED (light emitting diode), a sounding device or the like. 
   Reference numeral  56  denotes an electrically erasable and recordable non-volatile memory. For example, EEPROM (electrically erasable and programmable read only memory) or the like is used. Reference numerals  60 ,  61 ,  62 ,  64 ,  66  and  70  are operating sections, which are used for inputting various operation instruction signals of the system control circuit  50 . The operating sections are composed of one of or a combination of a plurality of a switch, a dial, a touch panel, a pointing by visual detection, an voice recognition apparatus or the like. 
   These operating sections  60 ,  61 ,  62 ,  64 ,  66  and  70  will now be described in detail. 
   Reference numeral  60  denotes a power switch for turning on and off a power source of the image processing apparatus  100 . Reference numeral  61  is a mode dial switch, which can switch and set various function modes such as an image sensing mode such as an automatic photographing mode, a manual photographing mode and a panoramic photographing mode, and a reproduction mode. 
   Reference numeral  62  denotes a shutter switch (SW 1 ), which is turned on during the operation of a not-shown shutter button, and instructs start of operation such as the AF (auto focus) processing, the AE (automatic exposure) processing, the AWB (auto white balance) processing and the EF (flash pre-light emission). 
   Reference numeral  64  denotes a shutter switch (SW 2 ), which is turned on upon completion of the operation of the above-mentioned not-shown shutter button. The shutter switch  64  instructs start of operation of a series of processing consisting of exposure processing for writing image data in the memory  30  by converting a signal read out from the image sensing device  12  through the A/D converter  16  and the memory control circuit  22 , development processing using operation in the image processing circuit  20  or the memory control circuit  22 , and recording processing for reading out image data from the memory  30 , compressing the image data in the compression and extension circuit  32  and writing the image data in a recording medium  200  and a recording medium  210 . 
   Reference numeral  66  denotes an image display on/off switch, which can set on/off of the image display  28 . With this function, power consumption can be reduced by blocking current supply to the image display consisting of the TFT-LCD or the like when an image is sensed using an optical finder  104 . Further, the setting of on/off of the image display  28  is stored in the memory  52  as an image display flag (on/off). The setting of the image display flag can be performed by the operating section  70  as a user desires. Further, The setting of on/off of the image display  28  may be stored in an internal memory of the system control circuit  50 . 
   Further, zooming of the image sensing device  10  is instructed by a not-shown zoom switch. 
   Reference numeral  70  denotes an operating section consisting of various buttons, touch panels or the like. The operating section  70  includes a menu button, a set button, a macro button, a multi screen reproduction page feed button, a flash setting button, a single shot/continuous shot self timer switching button, a menu shift/+ (plus) button, a menu shift − (minus) button, a reproduction image shift + (plus) button, a reproduction image shift − (minus) button, a menu shift up button, a menu shift down button, a photographing quality selection button, an exposure correction button, a data/time setting button or the like. 
   Reference numeral  80  denotes a power source control section, which is composed of a battery detection circuit, a DC-DC converter, a switch circuit for switching a block to be energized, or the like. The power source control section  80  detects loading of a battery, a type of a battery and a residual battery capacity, controls the DC-DC converter based on the detection result and an instruction of the system control circuit  50 , and supplies necessary voltage to each section including the recording media  200  and  210  for a necessary period. 
   Reference numerals  82  and  84  are connectors. Reference numeral  86  is a power source, which consists of a primary battery such as an alkaline battery or a lithium battery, a secondary battery such as an NiCd battery, an NiMH battery or an Li battery, an AC adopter or the like. 
   Reference numerals  90  and  94  are interfaces with the recording media  200  and  210  such as a memory card and a hard disk, and reference numerals  92  and  96  are connectors for connecting with the recording media  200  and  210  such as a memory card and a hard disk. 
   Reference numeral  98  is a recording medium insertion detection device, which detects whether or not the recording medium  200  or the recording medium  210  is inserted in the connector  92  or the connector  96 . 
   Further, this embodiment is described assuming that there are two systems of interfaces and connectors to which recording media are inserted. It is needless to mention that an interface and a connector in which a recording medium is inserted may be configured to be provided with either a single or a plurality of systems. In addition, an interface and a connector may be configured to be provided with different standards of interfaces and connectors in combination. 
   The interface and the connector may be configured using a medium conforming to a standard such as a PCMCIA card, a CF (compact flash) card or the like. In addition, if the interfaces  90  and  94  and the connectors  92  and  96  are configured using media conforming to a standard such as a PCMCIA card, a CF (compact flash) card or the like, image data and management information accompanying the image data can be transferred to and from other computers, peripheral equipment such as printers or the like by connecting various communication cards such as an LAN card, a modem card, a USB card, an IEEE1394 card, a P1284 card, an SCSI card and a communication card such as PHS. 
   Reference numeral  102  denotes the protective section  102  being a barrier, which covers an image sensing section including the photographing lens  10  of the image processing apparatus  100 , and thereby prevents stain or damage of the image sensing section. Reference numeral  104  is an optical finder, which can perform photographing using only this optical finder  104  without using an electronic finder function by the image display  28 . In addition, a part of the function of the display section  54 , for example, a focusing display function, a hand-shake alarm display function, a flash charge display function, a shutter speed display function, a focusing value display function and an exposure correction display function are provided in the optical finder  104 . 
   Reference numeral  110  denotes a communication section, which has various communication functions such as an RS232C, a USB, an IEEE1394, a P1284, an SCSI, a modem, an LAN and wireless communication. Reference numeral  112  is a connector or an antenna. It is a connector if the image processing apparatus  100  is connected with other apparatuses by the communication section  110 , and is an antenna in the case of wireless communication. 
   Reference numeral  200  is the recording medium such as a memory card and a hard disk. This recording medium  200  is provided with a recording section  202  composed of a semiconductor memory, a magnetic disk or the like, an interface (I/F)  204  with the image processing apparatus  100 , and a connector  206  for connecting with the image processing apparatus  100 . 
   Reference numeral  210  denotes a recording medium such as a memory card and a hard disk. This recording medium  210  is provided with a recording section  212  composed of a semiconductor memory, a magnetic disk or the like, an interface (I/F)  214  with the image processing apparatus  100 , and a connector  216  for connecting with the image processing apparatus  100 . 
   Reference numeral  400  denotes a flash device. Reference numeral  402  denotes a connector, which connects with an accessory shoe of the image processing apparatus  100 . Reference numeral  404  is a flash, which has a projecting function of AF auxiliary light and a flash adjusting function. 
   In such a configuration, if the image processing apparatus  100  is in the image sensing mode by the mode dial switch  60 , it is possible to sense an image using the shutter switch (SW 1 )  62  and the shutter switch (SW 2 )  64 . The system control circuit  50  is usually in a photographing preparation state. When it is detected that the shutter switch (SW 1 )  62  is pressed, the exposure control is applied by the exposure control section  40  and, at the same time, the distance measurement control is applied by the distance measurement section  42 . When these controls are completed, the system control circuit  50  shifts to an exposure starting state. Then, when it is detected that the shutter switch (SW 2 )  64  is pressed in this state, exposure is started. A sensed image obtained by photographing is stored in the memory  30  via the image sensing device  14 , the A/D converter  16 , the image processing circuit  20  and the memory control circuit  22 . The recorded image stored in the memory  30  is applied data compression by the compression and extension circuit  32  if necessary, and is stored in the memory  30  again. The system control circuit  50  is in the photographing end state here. 
     FIGS. 2 to 5  shows a flow chart of image sensing processing in this embodiment. 
   First, the system control circuit  50  initializes flags and control variables by an initial setting, that is, by turning on a power source such as exchanging a battery (step S 101 ). Then, the system control circuit  50  checks the state of the power switch  60  to determine whether or not the power switch  60  is set at ON (step S 102 ). If it is determined that the power switch  60  is set at OFF as a result of the determination, end processing is executed (step S 105 ). That is, predetermined end processing is performed such as changing display of each display section to the end state, closing the barrier of the protective section  102  to protect the image sensing section, recording parameters, set values and set modes including a flag, control variables or the like in the non-volatile memory  56 , and blocking an unnecessary power source of each section of the image processing apparatus  100  including the image display  28  by the power source control section  80 . The processing thereafter returns to the step S 102 . 
   On the other hand, if it is determined that the power switch  60  is set at ON as a result of the determination of the step S 102 , the system control circuit  50  checks the set position (the photographing mode or the reproduction mode) of the mode dial switch  61 , and determines whether or not the mode dial switch  61  is set at the photographing mode (step S 103 ). If it is determined that the mode dial switch  61  is set at the reproduction mode as a result of the determination, the system control circuit  50  executes the reproduction mode processing (step S 104 ), and the processing returns to the step S 102 . 
   On the other hand, if it is determined that the mode dial switch  61  is set at the photographing mode, the system control circuit  50  determines by the power source control section  80  whether or not there is a hindrance to operation of the image processing apparatus  100  judging from the residual capacity of the power source  86  and an operational state (step S 106 ) If it is determined that there is a hindrance to operation of the image processing apparatus  100  as a result of the determination, the processing advances to step S 109 . On the other hand, if it is determined that there is no hindrance to operation of the image processing apparatus  100 , the system control circuit  50  determines whether or not there is a hindrance to operation of the image processing apparatus  100 , in particular to record reproduction operation of image data for each of the recording media  200  and  210  judging from the operational state of the recording medium  200  or the recording medium  210  (step S 107 ). If it is determined that there is a hindrance to operation of the image processing apparatus  100  as a result of the determination, the processing advances to step S 109 . On the other hand, if it is determined that there is no hindrance to operation of the image processing apparatus  100 , the system control circuit  50  initializes the photographing lens  10  to determine whether or not the photographing lens  10  operates normally (step S 108 ). If it is determined that the photographing lens  10  does not operate normally as a result of the determination, the processing advances to step S 109 . 
   In step S 109 , the system control circuit  50  performs predetermined alarming display by images and voices using the display section  54  or the like. Then, the processing returns to step S 102 . 
   On the other hand, if it is determined that the photographing lens  10  operates normally as a result of the determination of the step S 108 , the system control circuit  50  determines whether or not an image display flag is set at ON (step S 110  of  FIG. 3 ). If it is determined that the image display flag is set at ON as a result of the determination, the system control circuit  50  checks an image display state of the image display  28  to determine whether or not the image display  28  is in the image display ON state (step S 118 ). 
   If it is determined that the image display  28  is not in the image display ON state as a result of the determination, the system control circuit  50  brings the image display  28  to the image display ON state (step S 119 ) and then a through display state, that is, a state in which sensed image data is sequentially displayed (step S 120 ), and the processing advances to step S 121 . On the other hand, if it is determined that the image display  28  is in the image display ON state, the processing advances to the step S 121  immediately. Further, in the above-mentioned through display state, data sequentially written in the image display memory  24  via the image sensing device  14 , the A/D converter  16 , the image processing circuit  20  and the memory control circuit  22  is sequentially displayed by the image display  28  via the memory control circuit  22  and the D/A converter  26 . Thus, the electronic finder function is realized. 
   In the following step S 121 , the system control circuit  50  determines whether or not the setting state display flag is set at ON. If it is determined that the setting state display flag is set at ON as a result of the determination, the system control circuit  50  display the setting state on the image display  28  (step S 122 ), the processing advances to step S 131  of  FIG. 4 . On the other hand, if it is determined that the setting state display flag is not set at ON, the processing advances to the step S 131 . 
   If it is determined that the image display flag is not set at ON (is set at OFF) as a result of the determination of the step S 110 , the system control circuit  50  determines whether or not the setting state display flag is set at ON (step Sill). If it is determined that the setting state display flag is not set at ON as a result of the determination, the processing advances to the step S 131 . On the other hand, if it is determined that the setting state display flag is set at ON, the system control circuit brings the image display  28  to the image display ON state (step S 112 ), displays the setting state on the image display  28  (step S 113 ), and determines whether or not the setting state display end time set in advance has come (step S 114 ). Then, the determination is continued until the setting state display end time comes and, if the setting state display end time comes, the setting state display flag is set at ON (step S 115 ), the setting state in the image display  28  is set at a non-display state (step S 116 ), the image display  28  is set at the image display OFF state (step S 117 ), and the processing advances to the step S 131 . 
   In the following step S 131  of  FIG. 4 , the system control circuit  50  determines whether or not the shutter switch (SW 1 )  62  is on. If it is determined that SW 1  is not on as a result of the determination, the system control circuit  50  determines whether or not the image display flag is set at ON (step S 152 ). If it is determined that the image display flag is set at ON as a result of the determination, the system control circuit  50  executes light measurement processing (step S 153 ) and the AWB processing (step S 154 ), and the processing returns to the step S 102  of  FIG. 2 . On the other hand, if it is determined that the image display flag is not set at ON, the processing returns to the step S 102  immediately. 
   If it is determined that the shutter switch (SW 1 )  62  is on as a result of the determination of the step S 131 , the system control circuit  50  executes the light measurement processing (step S 132 ). Further, in the light measurement processing, flash is also set if necessary. Then, the system control circuit  50  determines whether or not the image display flag is set at ON (step S 133 ). If it is determined that the image display flag is set at ON as a result of the determination, the processing advances to step S 135 . On the other hand, if it is determined that the image display flag is not set at ON, the system control circuit  50  performs the image sensing driving mode switching processing (step S 134 ), then the process advances to the step S 135 . In this image sensing driving mode switching processing, the driving mode of the timing generating circuit  18  is switched from a “normal reading mode” to a “partial reading mode”. These driving modes will be described. 
     FIG. 6  shows an image sensing area of an image sensing device, which corresponds to a display screen of one frame of a sensed image. 
   In the distance measurement processing, a high frequency component of a luminance signal obtained form the image sensing element  14  is obtained as a focus evaluating value, and a lens position indicating, for example, a maximum value of this focus evaluating value is regarded as a focusing point to perform focus adjustment. In that case, as shown in the figure, a part of an area of the screen is assumed to be distant measurement frames  410 ,  411  and  412 . In the normal reading out mode, a signal is read out from the entire image sensing area. A sensed image is displayed on the image display  28  based on the read out signal and a focus evaluating value is obtained based on the signal. That is, the normal reading out mode is a mode for performing photographing while displaying a sensed image on the image display  28 . 
   On the other hand, in the partial reading out mode, a signal is read out as usual only from a central area  402  where the focusing signed detecting areas  410 ,  411  and  412  are included, and high speed sweep off is performed for an upper area  401  and a lower area  403  shown in the figure. Thus, a focus evaluating value for one screen is obtained at high speed. That is, the partial reading out mode is a mode for performing photographing without displaying a sensed image on the image display  28 . The partial reading out mode requires less image sensing area to be an object of processing for obtaining a focus evaluating value compared with the normal reading out mode. As a result, burdens of processing are reduced. 
   Further, in the case in which the image processing apparatus  100  is used lengthwise, a high speed sweep off area in the partial reading out mode is also changed. That is, as shown in  FIG. 7 , a signal is read out as usual only from a central area  502  including focusing signed detecting areas  510 ,  511  and  512 , and high speed sweep off is performed for an upper area  501  and a lower area  503  shown in the figure. 
   Referring to  FIG. 4  again, in the following step S 135 , the distance measurement processing is performed in a set driving mode, and the focus of the photographing lens  10  is on a subject. Subsequently, the system control circuit  50  determines whether or not the image display flag is set at ON (step S 136 ). If it is determined that the image display flag is set at ON as a result of the determination, the processing advances to step S 138 . On the other hand, if it is determined that the image display flag is not set at ON, the system control circuit  50  performs the image sensing driving mode switching processing (step S 137 ), and then the processing advances to step S 138 . In this image sensing driving mode switching processing, the driving mode of the timing generation circuit  18  is switched from the “partial reading out mode” to the “normal reading out mode”. 
   In the following step S 138 , the system control circuit  50  determines whether or not the shutter switch (SW 2 )  64  is turned on. If it is determined that SW 2  is not turned on as a result of the determination, the system control circuit  50  determines whether or not the shutter switch (SW 1 )  62  is turned on (step S 139 ). If it is determined that SW 1  is not turned on (released) as a result of the determination, the processing returns to the step S 102 . On the other hand, if it is determined that SW 1  is turned on (maintaining the on state), the processing returns to the step S 138 . On the other hand, if it is determined that the shutter switch (SW 2 )  64  is turned on as a result of the determination of the step S 138 , the system control circuit  50  determines whether or not the image display flag is set at ON (step S 140  of  FIG. 5 ). 
   If it is determined that the image display flag is set at ON as a result of the determination, the system control circuit  50  sets the display state of the image display  28  at a fixed color display state (step S 141 ), and the processing advances to step S 142 . On the other hand, if the image display flag is set at ON, the processing advances to the step S 142  immediately. In this fixed color display state, replaced fixed color image data is displayed by the image display  28  via the memory control circuit  22  and the D/A converter  26  instead of the sensed image data to be written in the image display memory  24  via the image sensing device  14 , the A/D converter  16 , the image processing circuit  20  and the memory control circuit  22 . Thus, a fixed color image is displayed. 
   In the following step S 142 , the photographing processing is executed. That is, the system control circuit  50  performs exposure processing for writing photographed image data in the memory  30  via the image sensing device  14 , the A/D converter  16 , the image processing circuit  20  and the memory control circuit  22 , or via the memory control circuit  22  directly from the A/D converter  16 , and development processing for reading out the image data written in the memory  30  using the memory control circuit  22  and, if necessary, the image processing circuit  20  to perform various kinds of processing. 
   Subsequently, the system control circuit  50  determines whether or not an image display flag is set at ON (step S 143 ). If it is determined that the image display flag is not set at ON as a result of the determination, the system control circuit  50  brings the image display  28  to the image display on state (step S 144 ), and the processing advances to step S 145 . On the other hand, if it is determined that the image display flag at ON, the processing advances to step S 145  immediately. 
   In step S 145 , quick review display is executed. If the step S 144  is skipped, the image display  28  is in the state in which the image display  28  always displays a photographed image as an electronic finder, and quick review display immediately after photographing is also performed. On the other hand, if the processing gets through the step S 144 , the photographed image is displayed as a quick review for the first time immediately after photographing. 
   Subsequently, recording processing of the sensed image data is executed (step S 146 ). That is, the system control circuit  50  reads out the sensed image data written in the memory  30 , applies various kinds of image processing to the read out image data using the memory control circuit  22  and, if necessary, the image processing circuit  20 , and further applies the image compression processing to the image data according to a set mode using the compression and extension circuit  32 , thereafter writes the image data in the recording medium  200  or the recording medium  210 . 
   Subsequently, the system control circuit  50  determines whether or not the image display flag is set at ON (step S 147 ). If it is determined that the image display flag is set at ON as a result of the determination, the system control circuit  50  sets the display state of the image display  28  at a through display state (step S 148 ), and the processing advances to step S 149 . In this through display state, a sensed image is confirmed by the quick review display in the image display  28 , then image data sensed for the next photographing is sequentially displayed. 
   On the other hand, if it is determined that the image display flag is not set at ON as a result of the determination of the step S 147 , the system control circuit  50  sets the image display  28  at the image display off state (step S 150 ) and sets the setting state display flag at ON (step S 151 ), and the processing advances to the step S 149 . 
   In the following step S 149 , the system control circuit  50  determines whether or not the shutter switch (SW 1 )  62  is turned on. If it is determined that the SW 1  is turned on as a result of the determination, the processing returns to the step S 138  and the system control circuit  50  prepares for the next photographing. On the other hand, if SW 1  is not turned on (released), a series of photographing operation ends, and the processing returns to the step S 102 . 
   According to this processing, in photographing in the case in which an image display flag is set at ON, a sensed image is displayed on the image display  28  in the through display state(step S 120 ), and the distance measurement processing (step S 135 ) is performed in the normal reading out mode. On the other hand, photographing in the case in which the image display flag is not set at ON, although a setting state is once displayed on the image display  28 , the through display of the sensed image is not performed and the distance measurement processing is performed in the partial reading out mode. 
   According to this embodiment, in the case in which photographing is performed without displaying a sensed image, a focus evaluating value is obtained only from a signal in a central area including focusing signed detecting area by the partial reading out mode. Thus, a signal to be an object of reading out is limited, and as a result, burdens of processing are reduced and focus adjustment processing is performed promptly. Therefore, a shutter time lag can be shortened by reducing burdens of focusing processing at the time of photographing that does not require image display. 
   In addition, in the case in which photographing is performed while a sensed image is displayed, a focus evaluating value is obtained by the normal reading out mode. Thus, a signal of an entire area to be an object of image display is read out. Therefore, display of an appropriate sensed image can be secured by avoiding freeze or the like of a screen. 
   In addition, even with the partial reading out mode, since a reading out is an area including focusing signed detecting areas, accuracy of obtaining a focus evaluating value is never inferior. 
   In addition, with the partial reading out mode, prompt processing is secured without displaying a sensed image until photographing processing is completed, but the sensed image is displayed by quick review display for the next photographing after completing the photographing processing. Thus, convenience of use can be improved without preventing shortening of a shutter lag time. 
   As described above, according to this embodiment, a shutter lag time can be shortened by reducing burdens of focusing processing at the time of photographing that does not require image display. 
   In addition, it is possible to secure display of an appropriate sensed image by avoiding freeze or the like of a screen at the time of photographing that requires image display. 
   Further, it is needless to mention that the objects of the present invention can also be attained by supplying a storage medium in which a program code of software for realizing the above-mentioned function of each embodiment is supplied to an image sensing apparatus (the image processing apparatus  100 ), and a computer (or a CPU or an MPU) (the system control circuit  50 ) of the image sensing apparatus reads out and executes the program code stored in a storage medium. 
   In this case, the program code itself read out from the storage medium realizes the new function of the present invention, thus, the storage medium storing the program code constitutes the present invention. 
   As a storage medium for supplying a program code, for example, a floppy disk, a hard disk, an optical disk, an photomagnetic disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM or the like can be used. 
   In addition, it is needless to mention that this embodiment includes the case in which the above-mentioned function of each embodiment is realized not only by executing a program code read out by a computer but also by performing a part of or the entire actual processing performed by an OS or the like running on the computer based on an instruction of the program code. 
   Moreover, it is needles to mention that this embodiment includes the case in which a program code read out from a storage medium is written in a memory provided in a function extension unit connected to a computer or a function extension board inserted in the computer, then based on an instruction of the program code, a CPU or the like provided in the function extension board and a function extension unit performs a part of or the entire actual processing, thus the function of the embodiment is realized. 
   As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the claims.