The Basics design of a digital camera

A digital camera is similar to a film camera except that the film is replaced with an electronic sensor. The sensor is comprised of a grid of photo diodes, which change the photons that strike them into electrons. The electrons are stored in small buckets (capacitors) which are read out as a series of varying voltages and proportional to the image brightness. The voltage is converted to a number by an Analog to Digital Converter and the series numbers are stored and processed by a computer within the camera (Figure 1).
 
 

In many designs, a mechanical shutter is used in the same way that it is used in a film camera to control the light that is allowed to reach the sensor or film. Other cameras use what is called an electronic shutter, which allows the control of when the sensor gathers light through electronic control, signals to the sensor.

One Chip Camera - the "color 1 shot"

Figure 2

The "color 1 shot" camera uses a single 2 dimensional Photodiode array. The array is covered with a set of miniature color filters, red, green and blue, which cover individual pixels in a predefined pattern. Various patterns have been used. A popular pattern, called the Bayer pattern, uses a square for 4 cells that include 2 green on one diagonal, 1 red and one blue on the opposite diagonal (Figure 3).

One Chip / Three Shot Camera - the "color 3 shot"

   Figure 3

The "color 3 shot" camera uses a monochrome sensor and a rotating color filter wheel with 4 positions (Figure 4). The neutral position is used for focusing and composition and then three successive pictures are taken through each of the three filters: red, green and blue. The mImageä Digital Camera RGB3000 is based on this design (Figure 4).

Figure 4
 

The One Chip / Three Shot Camera - the "color 3 shot" design provides excellent resolution with no color aliasing (Figure 5). In addition, the Three Shot Camera has the advantage of allowing the use of either strobe or convention illumination. The availability of strobe allows greater flexibility of the use of the aperture for depth of field. Because of each color image require to shot three times, this type of camera can only shoot stationary objects in color but it can shoot moving objects in monochrome.

Figure 5