How Digital Cameras Work

How Digital Cameras Work
In the past several years most of the major technological advances in home electronics Have been based on Digital technology, that is converting analog information into digital data, represented by 1s and 0s or bits. This break through has changed how audio and video Information is processed. Ultimately the CD players , DVD players, HDTV, MP3 players, digital cameras, and DVRs are developed around digital technology.

The digital camera is very different from its predecessor. Conventional film cameras rely on Mechanical and chemical processes. On the basic camera you would not need even a battery to operate. The digital cameras, on the other hand have a built in computer or Ò digital processor Ò and record the image into a bit map.
This new approach has been improved enormously in quality over the years and will eventually replace film cameras within the next few years. Following will be a brief description of what goes inside these digital based devices.

Fundumentals
A digital camera basically converts an image into a long string of 0s and 1s that would represent the tiny dots - or pixels -- that collectively make up the image. This is called digitization or sampling. Digital scanners work in a similar fashion. With a digital camera, the light that bounces off the object is sampled or digitized into a series of 0s and 1s.

Digital cameras like film cameras have a series of lenses that focuses light to create an image. In a film camera this light is focused on a light sensitive film. Unlike film cameras, In a digital camera, the light is focused on a semiconductor sensor that records light in electronic format. The computer then breaks the electronic information into digital data. At its most basic level, this is all there is to a digital camera. Just like a conventional camera. In the next few sections, we will go into more detail.

A Filmless Camera
The main difference between a digital camera and a film camera is that the digital camera has no film. Instead it has a sensor that concert light into digital signals.

There are two types of sensors used in todayÕs digital cameras: CCD and CMOS. CCD stands for charged coupled device. CMOS stands for complementary metal oxide semiconductor. CMOS sensors are most cost effective to manufacture than the CCD sensors. CMOS sensors are used in less expensive digital cameras. However it is expected that CMOS sensors improve in quality and become more popular in future.
CCD sensors will be the choice in the high end digital cameras for some time. Most of what will follow in this article as based on CCD technology but will also apply to CMOS cameras as well to a large degree.
The CCD is a collection of tiny light-sensitive diodes, which convert photons (light) into electrons (electrical charge). These diodes are called photosites. In a nutshell, each photosite is sensitive to light -- the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.

Image Sensors
As mentioned before, there are two types of sensors. CMOS sensors have been responsible for falling price of digital cameras and camcorders. Both of these sensors convert light into electronic signal. A sensor is basically a two dimensional array of thousands cells. Each cell will transform the light from small portion of the image that goes through it to an electronic signal.

CCD vs. CMOS Sensors
The difference between a CCD and CMOS sensor is how the values of each cell is read. In a CCD device, the charge is actually transported across the chip and read at one corner of the array. An analog-to-digital converter turns each pixel's value into a digital value. In most CMOS devices, there are several transistors at each pixel that amplify and move the charge using more micro wiring. The CMOS approach is more flexible because each pixel can be read individually. CCDs use a special manufacturing process to create the ability to transport charge across the chip without distortion. This process leads to very high-quality sensors in terms of fidelity and light sensitivity. CMOS chips, on the other hand, use completely standard manufacturing processes to create the chip -- the same processes used to make microprocessors. Because of the manufacturing differences, there are several noticeable differences between CCD and CMOS sensors.

CCDs consume as much as 100 times more power than an equivalent CMOS sensor. CMOS sensors traditionally consume little power. Implementing a sensor in CMOS yields a low-power sensor. CCDs, on the other hand, use a process that consumes lots of power. CCD sensors create high-quality, low-noise images. CMOS sensors, traditionally, are more noise sensetive. The light sensitivity of CMOS sensor is lower Photons hitting the chip hit the transistors adjacent to photo diode. CMOS chips can be fabricated on just about any standard silicon production line, so they tend to be extremely inexpensive compared to CCD sensors. CCD sensors have been mass produced for a longer period of time, so they are more mature. They tend to have higher quality pixels, and more of them. Based on these differences, you can see that CCDs tend to be used in cameras that focus on high-quality images with lots of pixels and excellent light sensitivity. CMOS sensors usually have lower quality, lower resolution and lower sensitivity. However, CMOS cameras are less expensive and have great battery life.