Abstract:
A camera connectable to an external device includes an image pick-up unit for picking-up an image and for generating a corresponding image signal, and a release switch. The release switch selectively may be set to perform one of a plurality of functions, where the function of the release switch can be changed by the external device connected to the camera.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a camera removably connected to an external connecting device such as a personal computer, a personal digital assistant (PDA: information terminal equipment) or a word processor, to a connecting device for use with a camera, and to such a camera system including such a camera and connecting device. 
     2. Related Background Art 
     A digital camera for digital recording is known such as shown in FIG.  7 . In FIG. 7, reference numeral  710  represents a card-type digital camera, and reference numeral  720  represents a general personal computer (hereinafter called a PC). The internal structures thereof are shown in block in FIG.  7 . 
     In the structures shown in FIG. 7, a subject image passed through a lens  701  of an optical system is picked up by an image pickup element CCD  711 , subjected to predetermined processes such as CDS and AGC, and amplified to a predetermined level by a pre-amplifier  713 . The analog image signal is then converted into a digital image signal by an A/D converter  714 , processed by a signal processing circuit  715 , and temporarily stored in a memory  716 . 
     The above-described operations are controlled by a controller  717  which also outputs an interrupt signal to a PC  720 . Upon reception of this interrupt signal, PC  720  performs an interrupt routine. 
     PC  720  is generally constituted of a CPU  721 , a main memory  722 , a display  723 , a mouse  724 , a keyboard  725 , an HDD  726 , an FDD  727  and a local bus  728 . 
     In such a conventional card-type digital camera system, the interrupt routine of PC  720  copies an image in the memory  716  into the main memory  722  under the control of CPU  721  of PC  720 . This copied image is displayed on the display  723  by an application program. If these operations are performed successively, a moving image can be displayed. If a space key of the keyboard is depressed during the display of a moving image, a still image can be saved in a clip board or in a disk medium such as a hard disk. 
     With such a conventional camera system of the type that a camera head unit and a camera card are interconnected by a cable, a still image can be picked up only by actuating a keyboard or mouse of the PC. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in order to solve the above problem and provides a camera capable of picking up a still image by actuating a release switch of the camera, a connecting device for such a camera and a camera system thereof. 
     According to one aspect of the present invention, a camera is configured as follows: 
     (1) A camera is removably connected to an external connecting device such that the function of a release switch of the camera can be changed by the connecting device connected to the camera. 
     (2) The camera described in (1), wherein the release switch performs a desired function, in accordance with selecting means in application software. 
     (3) The camera described in (1), wherein a medium stores the status of the release switch, and the status stored in the medium is changed as desired by selecting means provided in application software. 
     (4) The camera described in (3), wherein the medium is a disk. 
     (5) The camera described in (3), wherein the medium is a shared memory. 
     (6) The camera described in (1), wherein an interrupt signal is sent to the connecting device upon actuation of the release button, and in response to the interrupt signal the connecting device processes an image signal picked up by the camera. 
     According to another aspect of the present invention, a camera connecting device is configured as follows: 
     (7) A connecting device is removably connected to a camera, and includes input means having the same function as a release switch of the camera. 
     (8) A connecting device is removably connected to a camera, and includes means for detecting whether the camera is equipped with a release switch. 
     According to still another aspect of the present invention, a camera system is configured as follows: 
     (9) A camera system includes a camera and a connecting device removably connected to the camera, the system includes means for detecting whether a camera with a release switch or a camera without a release switch is connected in the system. 
     (10) The system described in (9) wherein, the system is adapted to start up a photographing operation by the release switch of the camera, when the camera having the release switch is connected. 
     (11) The system described in (9), wherein a display of the detecting means is changed in accordance with a detection to whether a camera with a release switch or a camera without a release switch is connected in the system. 
    
    
     Other objects and features of the present invention will become more apparent from the following detailed description the preferred embodiments when read in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the structure of a camera system of this invention. 
     FIG. 2 is a flow chart illustrating the operation of a camera side according to a first embodiment of the invention. 
     FIGS. 3A and 3B are flow charts illustrating the operation of a connecting device side according to the first embodiment of the invention. 
     FIG. 4 is a flow chart illustrating the operation of a connecting device side according to a second embodiment of the invention. 
     FIG. 5 is a flow chart illustrating the operation of a connecting device side according to a third embodiment of the invention. 
     FIGS. 6A and 6B are flow charts illustrating the operation of a connecting device side according to a fourth embodiment of the invention. 
     FIG. 7 is a block diagram showing the structure of a conventional camera system. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 is a block diagram showing the structure of a camera system of the invention, the structure being basically the same as that of the system shown in FIG.  7 . 
     In FIG. 1, reference numeral  101  represents a lens of an optical system for focussing a subject image, and reference numeral  110  represents a card-type digital camera capable of being removably mounted on a card slot of a PC  120  which is an external connecting device. The camera  110  has an electrical circuit for interconnecting the optical system and PC  120  together. 
     In the card-type digital camera  110 , reference numeral  111  represents an image pickup CCD for converting a subject image (optical image) passed through the lens  101  of the optical system into an electrical signal. Reference numeral  112  represents a correction circuit for performing predetermined signal processing such as CDS and AGC. Reference numeral  113  represents a pre-amplifier for amplifying the signal corrected by the correction circuit  112 . Reference numeral  114  represents an A/D converter for converting the amplified analog image signal into a digital image signal. Reference numeral  115  represents a signal processing circuit for performing predetermined digital signal processing. Reference numeral  116  represents a writable memory, reference numeral  117  represents a controller for controlling the whole operation of the camera system, and reference numeral  118  represents a release button (switch). 
     In PC  120 , reference numeral  121  represents a CPU for controlling the entire operation of the PC, reference numeral  122  represents a main memory, reference numeral  123  represents a display for displaying various information, reference numerals  124  and  125  represent a mouse and a keyboard, respectively, as input means, reference numeral  126  represents an HDD, and reference numeral  127  represents an FDD. These elements are connected via a local bus  128  to the controller  117 . 
     The external connecting device such as PC  120  may be a PDA, a word processor or the like. In this embodiment, a PC is used by way of example. 
     Next, the operation of the camera system of the first embodiment will be described with reference to FIGS. 2,  3 A and  3 B. 
     FIG. 2 is a flow chart illustrating the operation of release means on the camera side. After a power of the camera  110  is turned on at Step S 201 , it is checked at Step S 202  whether the release button  118  is depressed. If depressed, the flow advances to Step S 203 , whereas if not, the flow remains in a continuous loop at Step S 202  to monitor a depression state of the release button  118 . 
     At Step S 203  the controller  117  sets a release flag to an interrupt signal. Next at Step S 204  an interrupt request is issued to the PC side. At Step S 205  an interrupt process is performed on the PC side to thereafter terminate this process. 
     FIGS. 3A and 3B are flow charts illustrating the operation to be performed on the PC (connecting device) side, this operation corresponding to the interrupt process at S 205  on the PC side shown in FIG.  2 . FIG.  3 A illustrates the processes of device driver software and application software, and FIG. 3B illustrates a freeze process. 
     When the interrupt process starts at Step S 301 , it is checked at Step S 302  whether the release flag is set. If set, the flow advances to Step S 303 , whereas if not, the flow advances to Step S 304  whereat the release interrupt process of the device driver software is terminated. 
     At Step S 303 , a message “WM_RELEASE” is output (PostMessage) to the application software. PostMessage is a standard function of Windows API for sending a message to an application. Windows API is an application programming interface of MICROSOFT WINDOWS (registered trademarks or trademark of Microsoft Corporation). This message is not immediately processed by the application software but is loaded in a message queue. 
     Therefore, the message from the driver software does not synchronize with a freeze process (to be later described) of the application software. This message may be made synchronous. However, in this case, a message sent to each application is assigned uniquely so that the application which does not know this message cannot run. 
     When the application program starts at Step S 305 , the message is picked up (GetMessage) from the message queue at Step S 306 . At Step S 307  it is checked whether WM_RELEASE=TRUE. If true, the flow advances to Step S 308 , whereas if not, this release interrupt process is terminated at Step S 309 . 
     At Step S 308  the freeze process is performed to terminate this release interrupt process at Step S 309 . 
     The freeze process starts at Step S 310 . Before this operation, the display  123  of PC  120  is in a preview state. In this preview state, a moving image is continuously displayed on the display  123  by copying image data from the memory  116  of the card-type camera  110  to the main memory  122  of PC  120 . In this preview state, the main memory  122  of PC  120  is used temporarily and when new image data is copied, the contents of the main memory  122  are overwritten. 
     At Step S 311  image data in the memory  116  of the camera  110  is copied to the main memory  122  of PC  120 . This main memory is a semiconductor storage medium such as a DRAM, and image data in the main memory  122  may be copied later to a disk in the form of an image file. Next at Step S 312  the image data in the main memory  122  of PC  120  is displayed on the display  123  as a still image to terminate this freeze process at Step S 313 . 
     A second embodiment of this invention now will be described. In this embodiment, the application software is changed as shown in FIG. 4 in order to use the release button  118  of the camera  110  for the actuation of the freeze (release) process. 
     FIG. 4 is a flow chart illustrating an interrupt process on the PC side with device driver software, application software and an event from an input device. 
     When the interrupt process starts at Step S 401 , it is checked at Step S 402  whether the release flag is set. If set, the flow advances to Step S 403 , whereas if not, the flow advances to Step S 404  whereat the release interrupt process of the device driver software is terminated. 
     At Step S 403 , a message “WM_RELEASE” is output (PostMessage) to the application software. Such a message sent to each application is assigned uniquely so that an application which does not know this message cannot run. 
     When the application program starts at Step S 405 , the message sent in response to a mouse event, a keyboard event or from the driver software is picked up from the message queue at Step S 406 . This event was issued from the input device such as a mouse and loaded in the message queue in a first-in first-out (FIFO) manner in an OS application such as MICROSOFT® WINDOWS® 95 or another WINDOWS® system. At Step S 407  it is checked whether WM_RELEASE=TRUE. If true, the flow advances to Step S 408 , whereas if not, this release interrupt process is terminated at Step S 409 . 
     At Step S 408  a freeze process is performed to terminate this release interrupt process at Step S 409 . 
     As above, a user can use the release request of the camera and the freeze request of the application software as release buttons of the same function, since both requests are processed as the same request. 
     Next, a third embodiment of the invention will be described. The application program is changed as shown in FIG. 5 to selectively set the release button  118  of the camera  110  to have a desired function such as saving a still image into a disk, saving a still image into a clip board, or not saving a still image. 
     FIG. 5 is a flow chart illustrating the interrupt process on the PC side with device driver software and application software. 
     When the interrupt process starts at Step S 501 , it is checked at Step S 502  whether the release flag is set. If set, the flow advances to Step S 503 , whereas if not, the flow advances to Step S 504  whereat the release interrupt process of device driver software is terminated. 
     At Step S 503 , a message “WM_RELEASE” is output (PostMessage) to the application software. When the application program starts at Step S 505 , a desired function is selected from a menu supplied by the application program at Step S 506 . If the still image is to be saved in the disk, diskFlag=ON and clipFlag=OFF are set. If the still image is to be saved in a clip board, diskFlag=OFF and clipFlag=ON are set. If the still image is not to be saved, diskFlag=OFF and clipFlag=OFF are set. 
     Next at Step S 507  the message from the driver software is picked up from the message queue. At Step S 508  it is checked whether WM_RELEASE=TRUE. If true, the flow advances to Step S 509 , whereas if not, this release interrupt process is terminated at Step S 513 . 
     If diskFlag=ON at Step S 509 , the flow advances to Step S 511 , whereas if not, the flow advances to Step S 510 . If clipFlag=ON at Step S 510 , the flow advances to Step S 512 , whereas if not, the flow advances to Step S 513 . At Step S 511 , the still image is written in the disk which may be a hard disk, a floppy disk, a removable hard disk flash disk, compact flash disk, or a magnetooptical disk. 
     At Step S 512  the still image is written in a clip board used as a system shared memory provided by an OS application such as MICROSOFT® WINDOWS® 95. By using this clip board, the still image may be pasted to another application or the like. 
     As above, a user selects a desired function from the menu supplied by the application program so that the function of the release button  118  of the camera  110  can be selectively set to one of saving a still image into a disk, saving a still image into a clip board, and not saving a still image. 
     Next, the fourth embodiment of the invention will be described. The application program is changed as shown in FIGS. 6A and 6B to allow discrimination between a camera with a release button and a camera without a release button. 
     FIGS. 6A and 6B are flow charts illustrating the operation of the interrupt process on the PC side. FIG. 6A illustrates the operation to be executed by the camera, device driver software and application software, and FIG. 6B illustrates the contents of a camera to be displayed. 
     As a camera  110  is loaded at Step S 601 , a haveReleaseSW is set at Step S 602  to thereafter terminate this camera side process. 
     As the driver software is activated at Step S 604 , information on a presence/absence of the release button  118  of the camera  110  is acquired at Step S 605 . If haveReleaseSW=(ON at Step S 606 , the flow advances to Step S 607 , whereas if not, the flow advances to Step S 608  to terminate the device driver process. 
     At Step S 607  a message “haveReleaseSW” is output (PostMessage) to the application software. As the application program starts at Step S 609 , the message is acquired from the message queue at Step S 610 . If haveReleaseSW=ON at Step S 611 , the flow advances to Step S 612 , whereas if not, the flow advances to Step S 615 . 
     At Step S 612  a resource for displaying a dialogue for selecting release means is set. In this case, the dialogue resource for selecting release means is set if haveReleaseSW=ON, and is not set if haveReleaseSW=OFF. 
     At Step S 613 , the dialogue for selecting release means is displayed. This dialogue is a kind of window generated either by an application with windows or an application without windows. 
     Next at Step S 614  the release means is selected to perform the freeze process at Step S 615 . This application program terminates at Step S 616 . 
     At Step S 617 , the release means may be selected by a mouse event or a keyboard event of the input device. The release operation may be performed by the camera or an input device such as a mouse or a keyboard at Step S 618 . 
     The contents in the storage medium of the camera are displayed at Step S 619 . The contents are haveReleaseSW=ON for a camera with a release button and haveReleaseSW=OFF for a camera without a release button. 
     As described so far, according to the present invention, it is possible to take a still image by operating the release button of a camera, although the keyboard or mouse of the connecting device has been used conventionally for this purpose. It is therefore possible to take a still image even if the connecting device and the camera head are positioned remotely. 
     Further, a user can perform the same function of taking a still image either from a freeze request of the application software (in response to an event issued from an input device such as a keyboard or a mouse) or from a release request of the camera. A user can therefore selectively use the one of them which is suitable for a particular image pickup environment. 
     Still further, the function of the release button can be selectively set as desired by the application software. 
     Still further, by providing means for discriminating between a camera with a release button and a camera without a release button, both cameras with and cameras without a release button can be used with the same driver and application software. 
     Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.