Abstract:
A digital camera having a camera body which includes a main surface and a lens surface substantially orthogonal to the main surface, a photographic lens of a photographic optical system positioned on the lense surface, and an optical viewfinder unit rotatably attached to the main surface such that the optical viewfinder unit is rotatable to a position substantially orthogonal to the main surface of the camera body and in a plane substantially parallel to said lens surface. An operation unit is positioned in the camera body such that operations buttons are arranged on the main surface of the camera body and, when the optical viewfinder unit is in a closed position, the operation buttons are substantially covered to protect against unintentional operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This document claims priority and contains subject matter related to Japanese Patent Application No. 11-080918 filed in the Japanese Patent Office on Mar. 25, 1999, the entire contents of which are incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a digital camera that stores image information obtained by an imaging device in a recording medium, and more particularly to a digital camera which is compact and has the convenience of portability. 
     2. Discussion of the Background 
     A camera using a photographic film (i.e. a silver halide film camera) has been generally used for photography. Recently, digital cameras have become increasingly widespread. In the digital cameras, object images, such as static images (still images) and moving images (movie images), are photographed by a solid-state imaging device, such as a charged coupled device (CCD) or the like, and image data of the object image are obtained and digitally recorded in a recording medium such as an IC (integrated circuit) card, a printed circuit (PC) card with semiconductor memory, a video floppy disk, or the like. 
     In the above-described digital camera, almost all functions, except for optical sub-systems, are digitally performed, including basic photographing functions, add-on accessory functions, etc. Because image data is digitally recorded in the recording medium instead of a photographic film, spaces for a film feeding unit and a film winding mechanism are not necessary in the digital camera. Therefore, a layout of each functional element of the digital camera can be more flexibly made, and the size of the digital camera can be more compact than that of the camera using a photographic film. Moreover, operability, portability, and appearance of digital camera can be enhanced by contriving to appropriately design the layout of each element of the digital camera. 
     Because a camera is usually equipped as a portable device for photographing various events, demand for a compact camera has increased. For example, the “one-time-use camera” or “disposal camera” using a photographic film has come into widespread use. This type of camera is made handy, and low in cost by reducing functions of the camera. 
     Similarly, with the widespread use of the digital camera, there is an increasing demand for a handy, portable, and low-cost digital camera. 
     In order to reduce the size of the digital camera, main elements of the digital camera need to be miniaturized including a photographic optical system, an imaging device, a recording medium, a digital circuit unit, a power supply battery, etc. Moreover, a viewfinder for confirming a photographing range, which is likely to occupy a relatively large space in the digital camera, also needs to be compact in the digital camera. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of the present invention is to provide a novel digital camera which is compact and has the convenience of portability. 
     Another object of the present invention is to provide a novel digital camera which has a simple configuration and is low in cost. 
     The digital camera of the present invention includes a camera body having a main surface and a lens surface substantially orthogonal to the main surface, a photographic lens of a photographic optical system, the photographic lens positioned on the lense surface, and an optical viewfinder unit rotatably attached to the main surface such that the optical viewfinder unit is rotatable to a position substantially orthogonal to the main surface and in a plane substantially parallel to the lens surface. 
     In one embodiment, the optical viewfinder unit includes a planar structure having a square shaped optical viewfinder window which serves as a field frame for defining a range of an object image, the main surface includes first and second opposing edges and the optical viewfinder unit is rotatably attached to the main surface at an axis parallel to and in the vicinity of the second edge, and a length and width of the optical viewfinder window are set according to a field angle of the photographic lens and a width of the camera body defined by a distance from the first edge to the second edge of the main surface. 
     In another embodiment, the digital camera further includes a view plate rotatably attached to the main surface at an axis in the vicinity of the first edge such that the view plate is moveable to a position substantially orthogonal to the main surface and substantially parallel to the surface of the optical viewfinder window, the view plate having a hole positioned such that a center of the hole is substantially in line with an orthogonal line extending from a center of the optical viewfinder window. 
     In yet another embodiment, the optical viewfinder unit includes a planar structure having a square shaped optical viewfinder window, at least one transparent member positioned in the optical viewfinder window, and a pattern of marks printed on the at least one transparent member and configured to assist a user of the digital camera in defining a photographing range of an object image. The at least one transparent member may be a single transparent member having a predetermined thickness and having the pattern of marks printed on opposing sides of the transparent member, or alternatively may be two or more transparent members each having a portion of the pattern of marks printed thereon. The position of the pattern of marks is determined according to the thickness of the transparent member or the distance between transparent members, and a field angle of a photographing lens of the photographic optical system. 
     In yet another embodiment of the present invention, the optical viewfinder unit is rotatable from a closed position wherein the optical viewfinder unit is in planar contact with the main surface, to an open position wherein the optical viewfinder unit is in the position substantially orthogonal to the main surface and in a plane substantially parallel to the lens surface, and the digital camera includes a power switch configured to be in an on state when the optical viewfinder is in the open position, and in an off state when the optical viewfinder is in the closed position. 
     In still another embodiment, the digital camera includes an operation unit having at least one operation button arranged on the main surface, wherein when the optical viewfinder unit is in the closed position, the at least one operation button is covered and protected from unintentional operation. 
     Finally, another embodiment of the digital camera includes a release button of an operation unit is arranged on an upper surface of a camera body. The upper surface of the camera body is substantially orthogonal to a surface where an object lens of a photographic optical system is exposed. An optical viewfinder unit is rotatable around an axis that is provided in the vicinity of the edge of the upper surface, connecting to the edge of the surface where the object lens of the photographic optical system is exposed. The optical viewfinder unit rotates approximately 90-degree angle from the position in which the optical viewfinder unit is in planar contact with the upper surface of the camera body. When the optical viewfinder unit is in planar contact with the upper surface of the camera body, the optical viewfinder unit covers at least the release button of the operation unit. The optical viewfinder unit rotates to the position in which the optical viewfinder unit vertically stands relative to the upper surface of the camera body so that the optical viewfinder unit is used for confirming a photographing range of an object image. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view illustrating an outward appearance of a digital camera according to a first embodiment of the present invention when the digital camera is not in a photographing mode; 
     FIG. 2 is a perspective view illustrating an outward appearance of the digital camera according to the first embodiment of the present invention when the digital camera is in the photographing mode; 
     FIG. 3 is a perspective view of the digital camera according to the first embodiment of the present invention in which square frames are printed on transparent members; 
     FIG. 4 is a perspective view of the digital camera according to the first embodiment of the present invention in which L-shaped marks are printed on the transparent members; 
     FIG. 5 is a perspective view illustrating an outward appearance of a digital camera according to a second embodiment of the present invention when the digital camera is in a photographing mode; 
     FIG. 6 is a perspective view illustrating an outward appearance of a digital camera according to a third embodiment of the present invention when the digital camera is in a photographing mode; and 
     FIG. 7 is a block diagram illustrating an electrical system configuration of the digital camera of FIGS. 1 through 6 of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, embodiments of the present invention are now described. FIG. 1 is a perspective view illustrating an outward appearance of a digital camera according to a first embodiment of the present invention when the digital camera is not in a photographing mode. FIG. 2 is a perspective view illustrating an outward appearance of the digital camera according to the first embodiment of the present invention when the digital camera is in the photographing mode. The digital camera illustrated in FIGS. 1 and 2 includes a camera body  1 , an optical viewfinder unit  2 , a photographic optical system  3 , a release button  4 , a photographing mode button  5 , a transmission button  6 , a display unit  122 , and a chain (or a strap)  7 . 
     The camera body  1  is formed, for example, in the shape of an approximately rectangular solid and includes a chain attaching part  1   a  on one side surface thereof. For the convenience of portability, the camera body  1  is formed in a compact rectangular solid of about 60 mm (length)×about 40 mm (width)×about 15 mm (height). 
     Provided on an upper surface of the camera body  1  is the optical viewfinder unit  2 . Further, the photographic optical system  3  is provided to one side surface of the camera body  1  such that an object lens of the photographic optical system  3  is visible from the outside of the camera body  1 . The optical viewfinder unit  2  is rotatably hinged on the upper edge of the side surface where the object lens of the photographic optical system  3  is exposed. Moreover, the optical viewfinder unit is of simple construction and provides a view of the actual image to be photographed as opposed to using a Liquid Crystal Display or other electronic device to generate or display an image being photographed or captured. This construction allows the digital camera of the present invention to be compact and light weight. 
     Specifically, the optical viewfinder unit  2  is rotatable around an axis which is provided in the vicinity of and parallel to the edge of the upper surface of the camera body  1 . The optical viewfinder unit  2  rotates approximately 90-degrees from the position in which the optical viewfinder unit  2  is in intimate planar contact with the upper surface of the camera body  1  (hereinafter referred to as the closed position) to the position in which the optical viewfinder unit  2  vertically stands (hereinafter referred to as the opened position). Although it is not shown, a mechanism for locking the optical viewfinder unit  2  at the opened position is provided in the camera body  1  to prevent the optical viewfinder unit  2  from unintentionally rotating from the opened position to the closed position. Further, a power supply switch (not shown in FIGS. 1 and 2, but indicated by reference numeral  130  in FIG. 7) is provided in the camera body  1  and is switched on and off in response to the operation of the optical viewfinder unit  2 . Specifically, the power supply switch  130  is configured to turn on a power supply (not shown) of the digital camera when the optical viewfinder unit  2  reaches the opened position and vertically stands to the upper surface of the camera body  1 , and is configured to turn off the power supply of the digital camera when the optical viewfinder unit  2  reaches the closed position. 
     In the optical viewfinder unit  2 , a transparent optical viewfinder window  2   a  is formed in a square shape and is typically called an action viewfinder or a sports viewfinder. The transparent optical viewfinder window  2   a  includes two or more transparent members, such as glass or plastic, which are spaced apart from each other a predetermined distance. A pair of frame lines  20   a  for defining a photographing range of an object image is printed on each of the transparent members such that respective frame lines  20   a  are parallel to the sides of the transparent optical viewfinder window  2   a . The length of the frame lines  20   a  and the distance between the frame lines  20   a  on respective transparent members are determined according to the distance between the transparent members and a field angle of a photographing lens of the photographic optical system  3 . The user looks at an object image through the transparent optical viewfinder window  2   a , and can confirm the photographing range which is defined by adjusting a distance between the user&#39;s eye and the transparent optical viewfinder window  2   a  such that respective frame lines  20   a  on the front and back transparent members are overlaid. In order for the user to more easily confirm the photographing range, a pair of lines connecting both ends of the frame lines  20   a  to form square frames  20   b  may be printed on the respective transparent members as illustrated in FIG.  3 . The square frames  20   b  may be printed on the respective transparent members in a similar manner. Alternatively, the transparent optical viewfinder window  2   a  may include only one transparent member having a predetermined thickness. Each pair of frame lines  20   a  may be printed on the front and back surface thereof. The length of the frame lines  20   a  and the distance between the frame lines  20   a  on respective transparent members are determined according to the thickness of the transparent member and the field angle of the photographing lens of the photographic optical system  3 . 
     Instead of the pair of frame lines  20   a  and square frames  20   b , various patterns of marks may be printed on the transparent member. On the transparent member in FIG. 4, L-shaped marks  20   c  are printed near four corners of the transparent optical viewfinder window  2   a , respectively, for defining the photographing range. Similar to the frame lines  20   a  illustrated in FIG. 2, the positions where the L-shaped marks  20   c  are printed on respective transparent members are determined according to the distance between the transparent members and the field angle of the photographing lens of the photographic optical system  3 . Alternative shapes of the L-shaped marks  20   c  may be employed, such as a circle. 
     Arranged on the upper surface of the camera body  1  are the release button  4 , the photographing mode button  5 , the transmission button  6 , and the display unit  122 . The release button  4  is used for executing a photographing operation (i.e., an image taking in/recording operation). The photographing mode button  5  is used for switching the photographing mode. The transmission button  6  is used for transmitting the data of a recorded image to an external computer (e.g., a personal computer) that is connected to the digital camera. The display unit  122  includes, for example, a liquid crystal display (LCD) device or a light-emitting device, and displays messages indicating the operational conditions of the digital camera, such as the photographing mode. 
     When the optical viewfinder unit  2  is closed (i.e., when the optical viewfinder unit  2  is in intimate contact with the upper surface of the camera body  1 ), the optical viewfinder unit  2  covers and protects the release button  4 , the photographing mode button  5 , and the transmission button  6  arranged on the upper surface of the camera body  1  from being unintentionally operated. 
     The chain attaching part  1   a  of the camera body  1  is used for attaching thereto the removable chain  7  (e.g., a key holding chain) for holding the digital camera. The user may hook the chain  7  on his or her clothing to carry the digital camera. 
     When the user does not photograph and carries the digital camera, as illustrated in FIG. 1, if the optical viewfinder unit  2  is closed to be in intimate contact with the upper surface of the camera body  1 , the optical viewfinder unit  2  covers and protects the release button  4 , the photographing mode button  5 , and the transmission button  6 . Further, as described above, the power supply switch  130  turns off the power supply of the digital camera. Therefore, erroneous operations of the digital camera can be avoided. Moreover, because the digital camera is compact in the closed condition, the user can carry the digital camera, for example, in a pocket or handbag. 
     When the user photographs, as illustrated in FIG. 2, the optical viewfinder unit  2  is opened so as to stand vertically to the camera body  1 . Further, as described above, the power supply switch  130  turns on the power supply of the digital camera when the optical viewfinder unit  2  is opened. Therefore, the user can confirm a photographing range of an object image in a clear and appropriate visual condition in the transparent optical viewfinder window  2   a.    
     Referring to FIG. 5, a digital camera according to a second embodiment of the present invention is described. FIG. 5 is a perspective view illustrating an outward appearance of the digital camera according to the second embodiment of the present invention when the digital camera is in a photographing mode. The configuration of the digital camera of the second embodiment is substantially the same as that of the first embodiment illustrated in FIGS. 1 and 2 except the optical viewfinder unit  2 . The optical viewfinder unit  2  of the digital camera of the second embodiment includes a square-shaped optical viewfinder window  2   b  in which no transparent member is provided. In other words, the optical viewfinder window  2   b  serves as a field frame. The length and width of the optical viewfinder window  2   b  are set according to the field angle of the photographic lens of the photographic optical system  3  and the width of the camera body  1  indicated by reference character a&#39; in FIG.  5 . The user looks at an object image through the optical viewfinder window  2   b  to confirm the photographing range of the object image. More specifically, the user puts, for example, his/her nose at a position A in FIG. 5 such that the middle point between his/her eyes is positioned substantially in line with an orthogonal line extending from the center of the optical viewfinder window  2   b , and the eyes arc substantially parallel to the surface of the optical viewfinder window  2   b . A view illustrating an outward appearance of the digital camera of the second embodiment when the digital camera is not in a photographing mode is omitted, because the view is substantially the same as FIG.  1 . 
     Referring to FIG. 6, a digital camera according to a third embodiment of the present invention is described. FIG. 6 is a perspective view illustrating an outward appearance of the digital camera according to the third embodiment of the present invention when the digital camera is in a photographing mode. A view illustrating an outward appearance of the digital camera of the third embodiment when the digital camera is not in a photographing mode is also omitted because the view is substantially the same as FIG.  1 . The configuration of the digital camera of the third embodiment is substantially the same as that of the second embodiment illustrated in FIG. 5 except the provision of a view plate  10 . The view plate  10  is configured to stand substantially parallel to the surface of the optical viewfinder window  2   b  and has a hole  10   a  such that the center of the hole  10   a  is positioned substantially in line with an orthogonal line extending from the center of the optical viewfinder window  2   b . The diameter of the hole  10   a  is in a range of about 4 mm to about 7 mm. The view plate  10  is hinged to the edge of the upper surface of the camera body  1  which is opposite and substantially parallel to the other edge of the upper surface of the camera body  1  to which the optical viewfinder unit  2  hinged. The view plate  10  is rotatable approximately 90-degrees about an axis in the vicinity of the edge of the upper surface of the camera body  1  to which the view plate  10  is hinged. The view plate  10  vertically stands relative to the upper surface of the camera body  1  by rotating from a closed position (i.e., a position in which the view plate  10  is in intimate contact with the upper surface of the camera body  1 ). A mechanism (not shown) for locking the view plate  10  when the view plate  10  is in the opened position is provided in the camera body  1  to keep the view plate  10  vertically standing relative to the upper surface of the camera body  1 . When the user photographs, the user opens and rotates the optical viewfinder unit  2  and the view plate  10  to vertically stand relative to the upper surface of the camera body  1 , respectively, and to face each other in parallel. The user confirms a photographing range of an object image by looking at the object image through the hole  10   a  of the view plate  10  and the optical viewfinder window  2   b . Like the optical viewfinder window  2   b  of the second embodiment, the length and width of the optical viewfinder window  2   b  are set according to a field angle of a photographing lens of the photographic optical system  3  and the width a&#39; of the camera body  1 . Although the number of construction parts of the digital camera of the third embodiment is more than that of the digital camera of the second embodiment, it is easier for the user to confirm a photographing range of an object image using the view plate  10  with the hole  10   a.    
     The electrical system configuration of the digital cameras illustrated in FIGS. 1 through 6 is now described referring to FIG.  7 . The exemplary digital cameras according to the embodiments of the present invention photograph not only static images (i.e., still images) in a static image capture mode, but also moving images in a movie capture mode in which moving image and sound are recorded for a short time. 
     The digital camera illustrated in FIG. 7 includes a lens system  101 , a shutter mechanism  102 , a charge coupled device (CCD)  103 , a correlate dual sampling (CDS) circuit  104 , a first analog to digital (A/D) converter  105 , a digital signal processing unit  106 , a compression and decompression unit  107 , a first-in first-out (FIFO) memory  108 , a card interface (I/F)  109 , a PC card  110 , a microphone  111 , a first amplifier and filter (AMP/FILTER)  112 , a second analog to digital (A/D) converter  113 , a sound data compression and decompression unit  114 , a digital to analog (D/A) converter  115 , a second amplifier and filter (AMP/FILTER)  116 , a central processing unit (CPU)  121 , the display unit  122 , an operation unit  123 , a transmission unit  124 , a lens driver  125 , a signal generator (SG)  126 , a battery  128 , a DC-DC converter  129 , and a power supply switch  130 . 
     The photographic optical system  3  for image focusing includes the lens system  101  and the shutter mechanism  102 . The shutter mechanism  102  includes an aperture mechanism and a filter mechanism, and controls an exposure time when a shutter is released. The shutter mechanism  102  may include an auto focus (AF) mechanism. As the imaging device, the CCD  103  is used in this embodiment. The CCD  103  converts optical images, which are imaged through the photographic optical system  3 , into electrical signals. 
     The photograph process system of the digital camera for processing the optical image signals includes the CDS circuit  104 , the first A/D converter  105 , the digital signal processing unit  106 , the compression and decompression unit  107 , the FIFO memory  108 , and the CPU  121 . 
     The CDS circuit  104  reduces noise in the electrical signals output from the CCD  103 . The first A/D converter  105  converts the analog image signals, which are input thereto from the CCD  103  through the CDS circuit  104 , into digital image data. In further detail, the A/D converter  105  converts the signals output from the CCD  103  to digital signals through the CDS circuit  104  with an optimum sampling frequency. 
     The digital signal processing unit  106  separates the digital image data, which is input thereto from the A/D converter  105 , into a color-difference component and a luminance component, and then performs various processes on each component, including a correcting process and a pre-process for compression/decompression. The compression/decompression unit  107  compresses the image data with, e.g., an orthogonal transformation and a Huffman encoding, and decompresses the image data with, e.g., a corresponding Huffman decoding and an inverse orthogonal transformation in conformity with the Joint Photographic Expert Group (JPEG) standard. 
     Sound is converted to electrical signals by the microphone  111 . In the first AMP/FILTER  112 , the sound signals in a predetermined band are passed through the first AMP/FILTER  112  and are selectively amplified. The second A/D converter  113  then converts the sound signals which have passed through the first AMP/FILTER  112  to digital sound data with a sampling frequency which is more than double the frequency of the predetermined band. Then, the sound data compression and decompression unit  114  compresses and encodes the digital sound data. 
     The FIFO memory  108  is a temporary memory device, such as a dynamic random access memory (DRAM), static RAM, a flash memory, or the like. The FIFO memory  108  temporarily stores compressed image data and sound data therein. The compressed image data and sound data are read out by the card interface  109 , and are recorded in the PC card  110  serving as a record medium connected to the card interface  109 . The PC card  110  contains a semiconductor memory or a recognized equivalent for recording information. 
     The CPU  121  controls operations of each unit of the digital camera according to instructions from the operation unit  123 . As mentioned above, the display unit  122  includes, for example, a liquid crystal display (LCD) device or a light-emitting device, and displays messages indicating the operational conditions of the digital camera, such as the photographing mode. 
     When transmitting data to an external device such as, for example, a personal computer, the data recorded in the PC card  110  is read out through the card interface  109  and the FIFO memory  108 , decompressed by the compression/decompression unit  107 , and then provided to the external device through the digital signal processing unit  106 . The sound data is decompressed by the sound data compression and decompression unit  114  through the FIFO memory  108 , converted to analog signals by the digital to analog (D/A) converter  115 , and is output through the second amplifier and filter (AMP/FILTER)  116 . 
     The operation unit  123  includes various operation devices, such as the release button  4  for inputting a photographing instruction, the photographing mode button  5 , and the transmission button  6  which are illustrated in FIG.  2 . The transmission unit  124  is controlled by the CPU  121  to transmit the image data output from the digital signal processing unit  106  and the sound data output from the second amplifier and filter (AMP/FILTER)  116  to an external device (e.g., a computer), when the transmission button  6  of the operation unit  123  is operated. 
     The lens driver  125  drives the photographing lens system  101  and the shutter mechanism  102  according to a control signal provided by the CPU  121 . The signal generator  126  generates drive control signals such as clock signals, and provides the drive control signals to the CCD  103 , CDS circuit  104 , and A/D converter  105  to drive each unit. 
     A power supply unit of the digital camera includes the battery  128  and the DC-DC converter  129 . As the battery  128 , a nickel cadmium battery, a nickel hydrogen battery, or a lithium battery is used. The voltage is converted to an appropriate level by the DC-DC converter  129  to be supplied to each unit of the digital camera. 
     As described above, the power supply switch  130  switches the power supply in response to the open/close operations of the optical viewfinder unit  2  relative to the camera body  1 . Specifically, the power supply switch  130  turns on the power supply of the digital camera when the optical viewfinder unit  2  is opened to vertically stand relative to the camera body  1 , and turns off the power supply of the digital camera when the optical viewfinder unit  2  is closed to be in intimate contact with the upper surface of the camera body  1 . The power supply switch  130  sends control signals to the CPU  121  to perform the on-off control of the power supply to each unit of the digital camera from the DC-DC converter  129 . 
     When the power supply switch  130  is turned on, the CPU  121  controls the photograph process system to be in a ready condition so that the digital camera is in the standby condition for photographing. In the photographing mode, the user confirms a photographing range of an object image by looking at the object image through the transparent optical viewfinder window  2   a  or the optical viewfinder window  2   b  of the optical viewfinder unit  2  in a clear and appropriate visual condition. After confirming the photographing range of the object image, the user depresses the release button  4  of the operation unit  123 , and thereby the object image is photographed in the desired photographing range. 
     In more detail, when the release button  4  of the operation unit  123  is depressed, the shutter mechanism  102  of the photographic optical system  3  is opened. Then, the object image is photographed with the CCD  3  through the lens system  101 . The image data of the object image is written in the PC card  110  through the digital signal processing unit  106 . 
     When the digital camera is in the standby condition for photographing, the user can select and set the photographing mode by operating the photographing mode button  5  and confirming the set of the photographing mode on the display unit  122 . Further, the user can transmit the photographed image data stored in the PC card  110  to an external computer through the transmission unit  124 . 
     When the user carries the digital camera, as illustrated in FIG. 1, the optical viewfinder unit  2  is closed to contact the camera body  1 , so that the release button  4 , the photographing mode button  5 , and the transmission button  6  on the upper surface of the camera body  1  are covered by the optical viewfinder unit  2 , and the power supply switch  130  is turned off. When the optical viewfinder unit  2  is closed, the digital camera including the camera body  1  and the optical viewfinder unit  2  is in a shape of a rectangular solid without projections on the outer surface of the digital camera. In this closed condition of the optical viewfinder unit  2 , because not only the release button  4 , the photographing mode button  5 , and the transmission button  6  of the operation unit  123  are not exposed but also the power supply switch  130  is turned off, an erroneous operation of the photograph process system can be prevented. Accordingly, the user can carry the digital camera without worrying about unintentional operations of the digital camera. 
     Because the above-described digital cameras according to the first through third embodiments include the optical viewfinder unit  2  of simple configuration for confirming a photographing range of an object image, the number of construction parts of the digital camera of the present invention is fewer than that of a digital camera including a liquid crystal display (LCD) for displaying photographed images. Therefore, a low-cost digital camera is obtained. 
     Further, because each optical viewfinder unit  2  according to the first through third embodiments also serves as the cover for the camera body  1 , the space for the optical viewfinder unit  2  is saved in the digital camera. Accordingly, the digital camera can be made compact and portable. 
     In the above-described digital camera, although it is configured such that the power supply of the digital camera is turned on or off in response to the opening or closing operation of the optical viewfinder unit  2  relative to the camera body  1 , the power supply may be turned on or off by manipulating a dedicated switch if the release button  4 , the photographing mode button  5 , and the transmission button  6  on the upper surface of the camera body  1  of the operation unit  123  are covered by the optical viewfinder unit  2 . 
     Moreover, in the above-described digital camera, the locking mechanism is provided to prevent the optical viewfinder unit  2  from being closed when the optical viewfinder unit  2  vertically stands to the camera body  1 . However, an alternative locking mechanism can be provided, in which a spring or other similar element is biased when the optical viewfinder unit  2  is rotated from the opened position to the closed position and the optical viewfinder unit  2  is locked in the closed condition. In this locking mechanism, the optical viewfinder unit  2  pops open when the optical viewfinder unit  2  is unlocked, and thus the digital camera quickly becomes ready for photographing mode. The above alternative locking mechanism is also applicable to the view plate  10  of the third embodiment. 
     Numerous additional 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 present invention may be practiced otherwise than as specifically described herein.