Idea and Research Book

How to Find Hidden Cameras - Carver Sindile

Sub-miniature camera modules are available for as cheap as $ 25 and even ready to use wireless sub-miniature cameras can be legally bought. Ease of use and the dropping prices highly contributed to the popularity of sub-miniature cameras. In effect highly miniaturized cameras can be bought, installed and operated even by the average citizen lacking financial resources and technical expertise.

Due to this it is not uncommon for sub-miniature cameras to turn up in places that are in fact neither public nor semi-public. The US company Given® Imaging has even developed an "Ingestible Imaging Capsule" for medical applications that is small enough to be swallowed. The capsule contains a color camera, batteries and a transmitter [21]. Given the size of those cameras it should be clear by now why naive attempts to find cameras will not yield reliable results.

Types of cameras and lenses

Sub-miniature photographic cameras exist as well, but those are not as popular as electronic cameras. This is because electronic cameras are more flexible to install and operate. They facilitate real time analysis and can be installed in places that are not easily accessible, since there is no need for changing films. On the other hand photographic cameras provide images far superior in quality to those of standard sub-miniature video cameras. Ancient electronic cameras used camera tubes to convert the virtual image of the filmed object to an electronic signal. There are several tube designs which all suffer from drawbacks such as high power consumption, sensitivity to mechanical stress, large size, short lifetime of the picture tube or high lag. Although there are still many tube based surveillance cameras in operation, they are of low importance concerning covert surveillance. Therefore this paper will focus on modern semiconductor based cameras. The camera does not need to be in the same room as the object under surveillance. It is possible to connect the primary lens to the camera by means of fiber optics, which are very similar to those used for medical applications. One advantage of this approach is that very little space is needed where the lens is to be installed. Another advantage is that detection of the lens can be made more difficult by using lens assemblies made of non conductive materials. Lenses prepared this way can not be detected with metal detectors. Still another advantage is that otherwise inaccessible rooms can be surveilled by feeding the fiber cable through sewage or air condition ducts.

CCD cameras

CCD2 cameras are much smaller than tube based cameras and consume far less power, typically two to five Watts. Particularly interesting for covert surveillance are sub-miniature CCD board cameras. Sub-miniature here means something like 32 mm square and 10 mm depth including lens and electronics. A "board camera" is a camera fully contained on a single circuit board including camera optics and all the electronics needed for generating the standardized video signal.
CCD cameras are available as monochrome (i.e. black and white) and (more expensive)
color versions. Several lenses are available such as tele ("zoom"), fish-eye (wide viewing angle) and pinhole. Pinhole lenses are small diameter fish-eye lenses of typically 2 mm or less in diameter. Pinhole lens cameras are particularly interesting for concealed surveillance applications because they can film through very small holes and even through light-weaved cotton. Monochrome cameras usually are more light sensitive (0.5 to 2 Lux) than their color counterparts (about 3 Lux). A pinhole black and white CCD board camera can bee seen in Fig. 2 at the right side.
Historically the major advantage of CCD cameras has been superior picture quality, but CMOS cameras (see below) are catching up rapidly. Compared to CMOS cameras, the CCD camera's disadvantages are large size, high power consumption and blooming. Blooming means "leakage" of bright pixels to neighboring pixels. Bright parts of the picture such as light sources facing the camera will look smeared. Another disadvantage is that CCD cameras can only be operated at temperatures below approximately 55 degrees Celsius [28]. In addition they have rather low dynamic range compared to CMOS cameras. This means that CCD cameras will fail to record very brightly lit and very dark objects at the same time. Bright parts of the picture will be overexposed while darker areas will only show black. Black and white CCD cameras are sensitive not only to human visible light but also
to radiation in the near infrared (IR) spectrum. This can be demonstrated by having the camera "look" into an active IR remote control as used for most TVs and VCRs. IR remote controls use light with a wavelength of approximately 900 nm. Light of this wavelength is invisible to humans but can be detected by black and white CCD cameras. The IR pulses that are emitted by the remote control can be seen as a flashing light on the video monitor. This offers some interesting possibilities. If an artificial source of IR radiation is supplied, monochrome CCD cameras can be used without any human visible light source. In effect such cameras can film in "complete darkness". The mentioned IR emitter can comprise several IR-LEDs4 grouped together, for example. Another possibility is to use a modified halogen floodlight with an IR pass filter applied to it. In some multiplex movie theaters there are CCD cameras and IR floodlights mounted at the ceiling above the screen, facing the audience. This enables personnel to take a look at what the audience is doing even in complete "darkness". Color cameras are sensitive to IR radiation as well, but in practice IR sensitivity is too low to be of any use.