Types of cameras and lenses:
There are many types of compact and hidden cameras available in the market, but they are not popular as much as the electronic cameras. The reason is that electronic cameras are easy to install and operate. They promote the real time analysis and can be used at the places that are not easy to access, since they do not require the changing of film. Also the electronic cameras give the super quality pictures as compared to the compact cameras whose picture quality is not very good.
The ancient electronic cameras used the camera tubes to transform the virtual picture of the filmed object to an electronic signal. There are different types of tubes, all having same issue such as high usage of power, vulnerable to mechanical pressure, time consuming and short lifetime of the picture tube. Nevertheless, still there are secret cameras in operation using the tube but they are of less importance.
It is not necessary that the camera should be in the same place as the place of the object. It is possible to connect the main lens to the camera by the help of the optical fibers which resembles just like an medical equipment. One advantage of this approach is that very small space is needed to install a lens. Another advantage is that the detection of the lens can be made tougher by using the lens assemblies which consist of non conductive material. Lens designed in this way cannot be located by the metal detectors. Still another feature is that the inaccessible rooms can be monitored by the use of optical fiber through the duct of split air conditioner.
These cameras are smaller than the tube cameras and consume very low power from 2-5 watts. These are very small in size about 30 mm in length and 10 mm in depth, especially designed for covert surveillance. These are also called board cameras. A board camera is a camera which is made of only single circuit which includes all the specifications to run a camera. CCD camera is available in black and white and it also comes in colored versions. Black and white cameras have a very little weight as compared to the colored ones. Different lenses can be used in these cameras such as tale, fisheye and pinhole. Pinhole lens is especially designed for closed monitoring applications because they can film from very small holes. The main features of the CCD cameras are the high quality image but the CMOS cameras are even better. As compared to the CMOS cameras, the CCD cameras are large in size, consume more power and blooming. Blooming here means mixing of pixels into one another. Shining part of the image facing the light of the camera will look streak. Another drawback is that CCD cameras can only be used at places where a temperature usually remains below 50 degree. Furthermore they have low dynamic range as compared to the CMOS cameras. This shows that these cameras are unable to record the shining and dark picture at once. Shining portion of the image will be overexposed while the dark one will be showing only black.
Monochrome CCD cameras are sensitive not only to the human vision but also to the radiation in the IR spectrum. This can be experimented by having the camera look into an operating infrared remote as used for the TV and VCR. The infrared remote uses the light with a wavelength of average 800nm. This range is not viewed by a normal human but can be detected by the monochrome CCD cameras. The infrared pulses that are emitted by the remote could be seen as an illuminating light on the screen of the TV. If a man made source of infrared radiation is provided, so black and white CCD cameras can be used without any visible light. So these cameras can work even in full absence of light. The infrared emitter can compare various infrared groups together. Another possibility is to use the advanced halogen beams with an infrared filter mixed with it. In some multiplex video theaters, there are CCD cameras and infrared beams mounted at the top of the screen, facing the audience. This allows the personnel to monitor the audience even in full darkness.
Another type of camera which can be seen on the top of the list in any catalogue is based on the CMOS technology. CMOS cameras were very few in the past years, but now they are very popular and customers used them as small web cameras. They are Available in black and white and colored version with various lenses such as pinhole and fisheye. Subminiature CMOS cameras do not come as board cameras, but rather they are packed in small plastic cases. They are lower in price then the CCD cameras. They consume less power and can be operated in high temperatures up to 120 degrees. They can be designed much smaller in size then the CCD cameras as major parts of the circuit can be built on the substrate that carries the light sensor. Similar to the CCD cameras, they are also sensitive to the infrared radiations. Furthermore they have a high dynamic capacity, the light and dark objects can be covered at the same time.
CMOS cameras have also some drawbacks. Because every pixel comes with a fragment of circuitry of its own which uses room and light, so the CMOS are not as light sensitive then CCD cameras. Another drawback is that the image quality is not good because each pixel is quite blurry. There are active pixel cameras available in the market which reduces the factor of noise but they are very costly then passive pixel cameras. CMOS cameras have many advantages over the CCD cameras in view to the noise if huge pixel array is to be formed. CMOS pictures are likely to surpass the CCD pictures in the near future.
These cameras are not much popular. As compared to the CCD and CMOS cameras, the appearance of the single picture is non-destructive. This enables the noise observation and reduction easy. The image quality is very good and there is no blooming. CID cameras include a broad spectrum from near infrared to UV. The pixels are not required to read at once so that combination of low and high light range is possible at a time. These cameras are more costly then the CCD and CMOS cameras. Up till now, they are very rarely used for the surveillance applications.