Generation and storage of amplified video

#Digital video cameras typically have optical elements, a photosensor, a data storage device, a controller and a display, all of which are generally mounted in a camera housing. Several types of photosensors are available for converting light to electrical signals in a digital video camera, such as a charge-coupled device (CCD) or an array of complementary metal-oxide semiconductor (CMOS) photodetectors. (The exemplary digital video camera discussed below will contain the latter, a photodetector array.)

#The optical elements typically include one or more lenses and/or reflectors. The optical elements focus an image of a scene onto the photodetector array. The photodetector array generates electrical image data representative of the image. The controller processes the image data and transfers it to and from the data storage device. The controller also transfers image data to the display and to output devices such as an external computer, a monitor, etc. Additionally, the controller may sequence the image data to produce video for playback at a later time.

#A typical photodetector array contains many photosensitive cells arranged in closely positioned rows and columns. Each photosensitive cell generates image data representative of a small portion of the image focused on the photodetector array. The image data generated by the photosensitive cells is combined to form the entire image, similar to a mosaic. Each photosensitive cell outputs a data value which corresponds to the intensity of light it receives over a given exposure time. The image data is buffered and later processed into a complete set of image data often referred to as a frame. Sequentially captured still frames are sequentially streamed together as video during a play event to show motion.

#Illustrative and presently preferred embodiments are illustrated in the drawing in which:

#FIG. 1 is an exemplary block diagram of a digital video camera.

#FIG. 2 shows a high level flowchart illustrating an exemplary algorithm for manually adjusting the gain of video image data.

#Generation and storage of amplified video enables a video camera to operate in low light environments by amplifying the signal carrying video image data and storing the resulting amplified image signal. A programmable variable-gain amplifier is placed in the image pipeline between the photodetector array (or its functional equivalent) and a storage medium. When the video camera detects a low light condition or a low level in the image signal, the variable-gain amplifier is programmed to amplify the image signal. The variable-gain amplifier may also be manually programmed if that feature is desirable in the video camera.

#The image signal can be amplified by the variable-gain amplifier as needed to produce visible details in the resulting individual image frames and overall video, even to the point at which it introduces color shift or noise in the image frames. Note that some color shift or noise in individual image frames will not be visible to most viewers of a video stream, because the persistence of the viewers eye tends to average out errors in individual image frames. In addition, it can be more important to the user to capture lower quality but bright and distinct video than high quality but overly dark video. Generation and storage of amplified video enables the video camera to maintain the maximum possible frame rate even in low light conditions and to minimize image smear due to subject motion. Generation and storage of amplified video can likely be performed using existing components in most video cameras, adding functionality with little cost.

#The exemplary embodiment described herein amplifies the image signals in a digital video camera. However, generation and storage of amplified video is not limited to use with a digital video camera, but may be used in any image capture device in which the image data can be electrically amplified, including non-digital video cameras, still cameras with video capture capabilities, etc.