A digital camera uses an electronic sensor such as a charge coupled device (CCD) to capture an image, a digital camera processor (DCP) to convert analog image signals from the CCD into digital image signals, a storage device to store the digital image signals, and a liquid crystal display (LCD) to display the digital image signals. The digital camera essentially includes four units including an image sensor used for receiving an optical image signal, which is further converted to digital image information, a lens unit used to form an image on the image sensor, a control device used for controlling all units in the digital camera to input/output image information or further process the image information, and a storage device is used for storing the digital image information. In a digital still camera, an image sensor, such as a CCD (charge coupled device), is arranged at the rear of a photographing optical system. A digital camera has a white balance adjustment function to correct the color balance of an image taken under various light sources. There are two kinds of lens shutters for digital still cameras, a normally closed shutter and a normally open shutter. Some digital cameras are provided with a sound memo function for recording sounds or voices as a sound data file in association with an image file, or a voice recorder for recording sounds as a sound data file independently of image data. These digital cameras are provided with a microphone for converting sounds into sound signals, and a speaker for reproducing the recorded sounds as well. Digital cameras provided with an optical finder include the separate type wherein light is directed to a finder without mediation of the taking lens. An AF (auto focus) mechanism is provided in the camera. A focused subject image is obtained by the AF mechanism. Many digital cameras also have an automatic flash device which measures reflection of a flashlight from a subject with photo sensor, and automatically stops emission of the flashlight when detects that a quantity of the reflection of the flashlight reaches a predetermined level. Digital cameras are provided with a rechargeable battery cartridge or power pack such as a rechargeable lithium ion cartridge. The rechargeable cartridge has a housing designed to fit and lock in place within a receiving cavity within the imaging device to be powered.

Digital cameras are equipped with a display such as a liquid crystal display. The LCD screen on a digital camera serves both in directing the camera when taking a photograph, and also for looking at and assessing the pictures already taken and stored in the camera. The display device is used to display regenerated or reproduced images photographed and recorded, and display images during photography. To view such images, the digital camera converts the image focused on the camera's image sensor device into electrical image data signals that are sent directly to the LCD. Such image data signals are sent to the LCD continuously and in rapid succession, such that the displayed image on the LCD appears as a live video image. The viewing of such a scene prior to the image being captured and stored on a removable memory device is called a preview or live view mode of operation. The user may capture a live view image by actuating the shutter button, which causes the image sensor device to generate electronic image data that is then stored in the camera's storage medium. The user can set the composition and confirm the focus state while viewing the displayed image during photography, and the display device functions as a video finder. When the image has been captured and stored on such a removable memory device, the LCD display may also be utilized to view the stored digital image in what is called a post view or review mode of operation where the captured image is retrieved from the removable memory device and displayed on the LCD screen. In addition to viewing stored images, the LCD is used to frame images for capture, similar to the viewfinder in a conventional photographic film camera. LCD screen on a digital camera is typically located on the rear of the camera's body or casing so that the screen is more or less flat with the rear of the camera.

A typical digital camera shoots a subject with a solid image pickup device such as an image pickup device, and obtains image data including a still image and/or a motion image. The image sensor may be of the charged-coupled device (CCD) or complementary metal-oxide semiconductor (CMOS) varieties. Most digital cameras employ charge-coupled device (CCD) image sensors. A digital still camera obtains image data sensing the image of the subject using a CCD and records the image data on a recording medium such as a memory card. The CCD device comprises the image pickup element, by means of an optical lens. The light energy is transferred into electrical signals by the CCD. A CCD that is used as an image pickup element senses brightness information only, and therefore a digital camera normally has color filters for individual pixels of the CCD so that the image information is separated into R (red), G (green) and B (blue) color data by means of these color filters, and then sensed.

A digital camera converts a photographed picture into a digital picture signal, compresses the digital picture signal, and records the compressed picture information to a record medium. A digital camera can also record a moving picture as well as a still picture. A digital camera functions by recording incoming light on some sort of sensing mechanisms and then processes that information to create a memory image of the target picture. In digital cameras, a distance from the camera to the object is measured by the distance measuring mechanism, and the image pick-up lens is driven in a direction of the optical axis depending on the measured distance to automatically focus the optical image of the object onto the light receiving surface of the CCD. The optical image of the object focused on the CCD is photoelectrically converted into analog signals. The analog signals are converted into digital signals which are then subjected to a prescribed image processing to form image data. The image data are displayed as a photographed image on the liquid crystal display. Digital cameras using an image sensor generally are capable of exposure control using image data read by the image sensor. A digital camera writes image data output from a large scale integrated circuit (LSI) for expansion to a frame memory when image data compressed and stored after imaging is reproduced. Generally, the resolution of an image captured by a digital camera is improved by increasing the pixel density of the image sensor. Pieces of the picture data are compressed in a predetermined format such as JPEG (Joint Photographic Expert Group) and are then recorded in an order they were photographed in the recording medium as picture files having file names each consisting of, for example, a date and time. Many digital cameras adopt a TTL photometry (through the lens photometry) system with high precision for a photometry to control exposure. The TTL photometry system measures brightness of a scene to be taken by using an output signal from an imaging device for taking the scene.

The digital camera is provided with a mode setting switch or the like in order to set the mode. The digital camera has various modes including a taking mode and a setting mode for setting various devices. The taking mode has an auto-taking mode, a manual-taking mode, a sequence-taking mode and a movie-taking mode. The setting mode has a driving condition setting mode for a liquid crystal panel used as an electric viewfinder and a monitor, a power-setting mode for auto power-off, a sound-setting mode for beeping sound, and a date and time adjusting mode. In a continuous shoot mode, multiple static images are successively obtained at a predetermined time interval when the operator continuously depresses a shutter release device. In an auto bracketing mode a same static image is photographed with different predetermined multiple exposure values corresponding to a shutter release operation. In a movie capture mode, the moving images are obtained each time the shutter releases in response to the shutter release device being continuously depressed. In the live view mode of operation, the scene to be previewed is repeatedly captured by a charged coupled device (CCD) and then buffered to the LCD to allow the image to be refreshed at some predetermined refresh rate or frames per second rate without the benefit of any long term memory storage device. In a setting mode, a digital still camera can be set to various image processing methods such as compression ratio, captured image size, amount of white balance adjustment, image sharpness, image brightness, monochrome or color photography and volume of alert tones. A digital camera having a playback function is capable of being set to an imaging mode and to a playback mode. If the playback mode is set, the desired frame is specified by a frame-forward button or frame-back button in such a manner that the desired frame will be reproduced. A digital camera can be set to a variety of shooting conditions such as shutter speed, f-stop number and amount of strobe light emission.

A digital image photographed by a digital camera is generally recorded in a recording medium such as a detachable memory card and a magnetic disk. Memory cards are manufactured in several types such as multimedia (MM) cards, secure digital (SD) cards and reduced size multimedia (RS-MM) cards for use in different types of digital cameras. A flash memory card is a nonvolatile memory device with a compact housing that does not require a power source in order to retain its memory contents. The memory card can directly and electrically get access to information with respect to a non-volatile memory formed in the semiconductor memory chip. Flash memory cards can provide "plug and play" capability, low power consumption, portability, and high density storage. Examples of memory cards include CompactFlash (CF), the Memory Stick (MS) and subsequent versions including Memory Stick Pro and Memory Stick Duo developed by Sony Corporation, Smart Media memory cards, Secure Digital (SD) memory cards, and MultiMedia Cards (MMCs), and xD digital memory cards. Many digital cameras provide an indication of the approximate number of images that could be stored on a memory card.