IMAGE SENSORS and SIGNAL PROCESSING for DIGITAL STILL CAMERAS (original) (raw)
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Comparison of CCD, CMOS and intensified cameras
Experiments in Fluids, 2007
The properties of digital cameras are often important to obtain accurate results with image based measurement techniques. Unfortunately, a detailed comparison of the sensor specifications and performance is not accessible as this information is normally not provided by the manufacturers and no generally accepted comparison standard exists. Therefore, a detailed quantitative comparison was performed to evaluate and assess the characteristics of state-of-theart CCD, CMOS and intensified CMOS sensors. These results may be of assistance when selecting the appropriate sensor for a desired application.
A digital file is data, no different to any other computer file. It can be saved to any computer storage media. The file can also be copied and recopied without any loss of quality. Copies can be kept in more than one picture library, or in other locations, all giving high-quality images. Image files can be opened on a computer using imaging software such as Adobe Photoshop. This allows dust spots and other minor blemishes to be removed quickly and easily. It is also possible to make more significant changes to an image, but this may not be acceptable in areas such as news, sport and wildlife. Almost all newspapers, magazines, books, brochures and other printed materials are now created on computers and use digital image files for their photographs. To meet this demand, most picture libraries now only accept digital images. Although it is possible to scan film transparencies to create digital files, it is more convenient to shoot digitally in the first place. The term analog refers to simple or SLR cameras, which uses film as the printing medium for photographs. They are then produced in analog, using a chemical process. Film cameras have the advantage of being relatively inexpensive as compared digital cameras of the same quality, but on the other hand, buying film and developing rolls can get expensive. Analog cameras have 35 mm film; hence light covering a bigger area than in digital cameras. The main disadvantage of an analog camera is for beginners; they would need to note down the camera settings, before actually taking pictures. Different effects on pictures, which result from developing, also need to be tracked. The most important advantage of an analog camera, the reason why most photographers choose it, is the picture quality. The picture quality that can be achieved with a film camera is very high and the images turn out extremely sharp. The reason behind this is the chemical reaction which takes place when light from the shutter falls on the film, and as a result an exact, crisp and inverted i.e. negative representation of the object is obtained. This is not possible with a digital camera. Digital photography is no different from film/analog photography, as matter of fact the technique and style used is the same, except for one aspect. The distinction between digital and analog photography is that traditional film is replaced by a charged coupled device (CCD), which contains tiny grids containing millions of photosensitive elements. When a picture is clicked, a ray of light falls on the photosensitive elements, which then registers a specific intensity of light, as an electrical charge. The electrical charges are then passed onto an analog-to-digital converter that transforms them into digital data. To determine the actual color value of any one pixel, the camera's software makes a calculated guess based on the values registered by three neighboring photosensitive elements. This is the reason which accounts for the reduction the image's level of detail, and eventually translates into the quality of image. Image Sensor An image sensor or imaging sensor is a sensor that detects and conveys the information that constitutes an image. It does so by converting the variable attenuation of waves (as they pass through or reflect off objects) into signals, the small bursts of current that convey the information.
Digital Photography - Image Sensors
A digital file is data, no different to any other computer file. It can be saved to any computer storage media. The file can also be copied and recopied without any loss of quality. Copies can be kept in more than one picture library, or in other locations, all giving high-quality images. Image files can be opened on a computer using imaging software such as Adobe Photoshop. This allows dust spots and other minor blemishes to be removed quickly and easily. It is also possible to make more significant changes to an image, but this may not be acceptable in areas such as news, sport and wildlife. Almost all newspapers, magazines, books, brochures and other printed materials are now created on computers and use digital image files for their photographs. To meet this demand, most picture libraries now only accept digital images. Although it is possible to scan film transparencies to create digital files, it is more convenient to shoot digitally in the first place. The term analog refers to simple or SLR cameras, which uses film as the printing medium for photographs. They are then produced in analog, using a chemical process. Film cameras have the advantage of being relatively inexpensive as compared digital cameras of the same quality, but on the other hand, buying film and developing rolls can get expensive. Analog cameras have 35 mm film; hence light covering a bigger area than in digital cameras. The main disadvantage of an analog camera is for beginners; they would need to note down the camera settings, before actually taking pictures. Different effects on pictures, which result from developing, also need to be tracked. The most important advantage of an analog camera, the reason why most photographers choose it, is the picture quality. The picture quality that can be achieved with a film camera is very high and the images turn out extremely sharp. The reason behind this is the chemical reaction which takes place when light from the shutter falls on the film, and as a result an exact, crisp and inverted i.e. negative representation of the object is obtained. This is not possible with a digital camera. Digital photography is no different from film/analog photography, as matter of fact the technique and style used is the same, except for one aspect. The distinction between digital and analog photography is that traditional film is replaced by a charged coupled device (CCD), which contains tiny grids containing millions of photosensitive elements. When a picture is clicked, a ray of light falls on the photosensitive elements, which then registers a specific intensity of light, as an electrical charge. The electrical charges are then passed onto an analog-to-digital converter that transforms them into digital data. To determine the actual color value of any one pixel, the camera's software makes a calculated guess based on the values registered by three neighboring photosensitive elements. This is the reason which accounts for the reduction the image's level of detail, and eventually translates into the quality of image. Image Sensor An image sensor or imaging sensor is a sensor that detects and conveys the information that constitutes an image. It does so by converting the variable attenuation of waves (as they pass through or reflect off objects) into signals, the small bursts of current that convey the information.
Standard CMOS active pixel image sensors for multimedia applications
arvlsi, 1995
The task of image acquisition is completely dominated by CCD-based sensors fabricated on specialized process lines. These devices provide an essentially passive means of detecting photons and moving image data across chip. We argue that line widths in standard ...
Comparison of Global Shutter Pixels for CMOS Image Sensors
In this paper we are presenting preliminary results from 4T technology based CMOS image sensors with global shutter, i.e. all pixels in the active array integrate light simultaneously. The global shutter operation mode is particularly important for high-speed video applications, where the more commonly implemented rolling line shutter creates motion blur. Our chips were fabricated using a 0.18 micron 4T, CIS technology with pinned photodiode and transfer gate. Different from conventional 3T type CMOS image sensors with global shutter pixel, in these 4T technology based global shutter pixels, the charge is transferred, not just sampled, onto the sense node. This translates into very high sensitivity and low readout noise at low power. For an imager with 7 transistors per pixel that is operated in global shutter, "Integrate While Read" mode, we measure an input referred noise of 10 electrons. The extinction ratio at full well signal charge is ~ 97.7%.
The comparison of CCD and CMOS image sensors
2008
abstract The architectures of CCD and CMOS image sensors are introduced briefly, followed by comparison of their performances in detail. At last, the future development trends of CCD and CMOS image sensors are prospected. It is pointed out that CCD and CMOS image sensors will remain complementary and competition, and flourish the image sensor market together in predictable future.
An Ultra-High Resolution Digital Camera
The Journal of Photographic Science, 1994
We are developing a camera capable of capturing images of fine art paintings of up to one metre square at a resolution of 20 pixels per mm, based on the Kon Iron ProgRes 3012 camera which uses piezo micro-adjustment of the CCD array to produce 3000 by 2320 pixels. The new camera will incorporate an X-Y translation stage that moves the array around the image plane to acquire blocks that can be mosaiced together to form the final large digital image.