|Sunday, 03 September 2006|
Along with the popularization of a high-speed data transmission in the radio network field, expectations on the multimedia is gradually increased also in the mobile phone field and it is anticipated that more and more multimedia application functions will be mounted on mobile phones in future. In this context, there is a tendency of an introduction of a picture phone function enabling real-time exchanges of voice data and image data. In recent years, manufacturers have introduced mobile devices with built-in cameras into the market. A mobile terminal device provided with an image capturing device such as a digital camera has been developed and practically used. The mobile terminal device provided with a digital camera has an image-information transmitting and receiving function in addition to a conventional voice-information and text-information transmitting and receiving function. Consumers may use their camera phones to capture images, send and receive digital images, and/or participate in a video teleconference. In general, a portable telephone may be classified according to its appearance. This may include, for example, a bar-type, a flip-type, and a folder-type portable telephone. Portable telephones may also be classified in accordance with the method in which they are worn, including, for example, neck wearable types and wrist wearable types. Portable telephones may also be classified according to their functionality such as, audio, video and Internet functionality. A camera phone is a combination of a cellular telephone and a camera in a single housing.
Camera phones comprise a mobile, hand-held telephone and a digital camera in the same physical package. Digital camera lenses are added as a feature on cellular telephones to allow users to communicate and exchange information through pictures. A camera phone combines an image capture device, an image display device, and a codec for coding and decoding the image. Thin cameras that may be mounted on portable telephones with camera have shorter lens moving distance for focus and zoom adjustments in photographing compared to other ordinary cameras. Some foldable mobile telephones with a camera function are so constructed as to expose the main display when the mobile telephone is opened outward. The main display shows a picture image taken by the camera section. The user shoots while monitoring the picture image on the main display. Contrarily, an unfoldable mobile telephone has a main display on the front surface, and has a camera section on the rear surface. The user can shoot monitoring picture images on the display while holding the mobile telephone with its longitudinal axis kept horizontally. Mobile phone cameras are meant to be used with the phone orientated vertically (in the orientation where it is used while using it as a phone). In that case the image sensor produces a horizontal picture. Some phones have a portrait mode which takes vertical pictures.
Since the digital camera for image pickup devices must be mounted in small mobile phones, technology of miniaturizing the digital camera is a key point. An externally mounted digital camera as well as an internally mounted digital camera is also used. The externally mounted digital camera is mounted at a portion of a body of a mobile phone to photograph an object in front or back of a liquid crystal display (LCD) window of the mobile phone while being manually rotated by a user. However, such an externally mounted digital camera is problematic in that it is inconvenient to use because a user always carries both a mobile phone and the digital camera, and uses the digital camera by attaching it to the mobile phone if necessary, and the total volume of the devices increases. Therefore, a mobile phone with an internally mounted camera is generally used. Currently, digital camera modules used in cell phone are becoming progressively more miniaturized over time, and digital camera modules are correspondingly becoming smaller and smaller. A cell phone with an electronic camera has a built-in taking lens and a viewfinder. The camera lens module comprises an image sensor provided on a printed circuit board and a lens holder fitted with an infrared filter (IR filter). When taking a picture by a portable phone with camera, the portable phone is often held with one hand to take a picture of the holder's face or other subjects in close proximity. For this reason, photographic lenses used in this type of camera often have a close-up photographing function.
Imaging devices, such as camera phones, use photodetector arrays to produce electronic signals that are capable of producing images output to a display or printer. A typical photodetector array has many individual photosites or picture elements (pixels), each of which is responsive over a relatively wide range of wavelengths. Recent image pickup elements are smaller and provide more pixels in a given detector area, which helps meet demands of higher resolution and more compactness that are especially required in imaging devices for digital cameras. Image pickup elements with megapixel detectors are being used practically. High performance is also increasingly demanded. An imaging device is also referred to as camera lens module. A CMOS image sensor is commonly used an image sensor. The CMOS image sensor is a device employing a switching system for sequentially detecting outputs using MOS transistors, which equals to the number of pixels. A CCD solid-state image sensor includes a matrix of photoelectric conversion elements, a plurality of vertical CCDs that are shift registers for reading out charge from photodiodes row by row and transferring them in the vertical direction, and a horizontal CCD that is a shift register for transferring, in the horizontal direction, the charge transferred from the plurality of vertical CCDs.