The first cameras used in several applications were the CCD type whose construction technology got them more expensive and there were still other difficulties in its use.
The technology currently used is the CMOS, where semiconductor materials chips sensitive to light produce a matrix with filters for many colors, as shown in Figure 1.
The important fact, however, is that we have these cameras in our mobile phones and they can be used for several purposes, besides they simply get images to the photos and the movies we want to make.
Many applications available on the Internet make use of the available camera, whether on Android as on another operating system.
We can take as an example the programs that read bar codes.
But for us who want to do electronic experiments using the camera it is important to know some important features.
One of them is the spectral curve. Knowing how the camera behaves on different colors is important. In Figure 4 we have a typical spectral curve of a CMOS camera.
As we can see, the sensors used can also sense radiation in the infrared range, and in some cases filters are used to avoid capturing it.
However, some applications can access the individual sensors of the camera and thus make it possible to choose the colors that are seen and even to detect infrared radiation, as we have seen in our article CEL001.
Several applications and experiments can be performed based on this fact, all depending on the reader's imagination.
We have seen on that article that there are applications that allow you to highlight the red, cutting other colors, and thus allowing a "thermal" night vision of the objects.
The experiment described precisely allows us "to see in the dark" an infrared LED or the signal emitted by a remote control.
But there is much more to be done.
A physics experiment, for example, can get LEDs in 3 different colors (RGB) and set the camera to "see" one at a time in the dark.
The experimenter will see that when the camera is set to see the green, even though the three are lit, only the green LED appears, looking like the others are off.
A program that converts the signal of infrared output to sound, for example, allows an optical telegraph communicator using the camera as a receiver.
If the signal can be decoded, we can modulate an infrared lamp on the ceiling with the sound signal from a TV and hear it in the cell phone that becomes the recipient of a "wireless phone".
Anyway, there are many interesting possibilities to explore the articles in this section.
Our suggestion is that the apps available on Google Play, the reader explores the one which makes use of the camera.
