Indoor and outdoor Wireless Camera pan/tilt platform and controllers

The joystick is moved forward or backward, left or right corresponding to the vertical (tilt) and horizontal (pan) movements of the camera/lens unit. Likewise, the thumb trackball is moved using the thumb to initiate pan and tilt. For the disk, touch-pad, and four-button design, left and right initiate panning, and top and bottom initiate tilt. The security officer watches the video monitor and can point the Wireless Camera to view any area within the pan/tilt rotation range. The platform and camera move in accordance with the control signal sent by the control unit. Pan/tilt platforms are available in a wide range of sizes from lightweight, pan-only units (scanners) for indoor applications to heavy-duty, environmentally protected pan/tilts for outdoor applications. Rugged outdoor units are environmentally enclosed and intended to withstand severe conditions of temperature, precipitation, dust, humidity, and high winds.

In the late 1990s the requirement for faster, more compact, and discreet PTZ surveillance cameras surfaced from casino, retail store, warehouse, and other applications. This resulted in the development of the high-speed video-dome camera system. The technology that made this innovation possible was the availability of small, high resolution, high sensitivity CCD camera sensors and associated DSP electronics. This, in turn, permitted the use of smaller zoom lenses. The Sony and Hitachi companies then developed the core component of the highspeed dome camera: a unitized digital pan/tilt drive package surrounding the miniature camera/lens assembly. 

There are three primary applications for pan/tilt units:

(1) monitoring a fixed or point site, (2) monitoring an area site, and (3) monitoring a volume site.

A point site might correspond to a bank teller, where the area of interest is the teller and customer, and the business transaction. An area site might be a building lobby where the activity in the lobby is of interest. A volume site might be a warehouse where many vertical bays (levels) must be under surveillance at different times. For the fixed or point site, a single fixed camera and lens are suitable to view the entire area. In the area and volume cases, a single fixed camera cannot see the entire area of interest, so a panning and tilting camera and a zoom lens are required.

Applications that use pan/tilt mechanisms can be roughly classified into indoor and outdoor types, mounted in either an overt configuration—without a concealing dome or housing—or a covert application, where the pan/tilt mechanism and lens/camera unit are hidden in a dome, hidden behind some visually opaque window, or camouflaged by some other means. A common type used in indoor applications consists of a panning platform that rotates the camera via direct operator control or automatically pans from side to side to cover the specific area. A second type is the pan/tilt unit in which panning and tilting are done manually (under operator control) or automatically. Both types can be augmented with a remotely controlled zoom lens to change the FOV and therefore the instantaneous camera coverage within the full range of the scanner or pan/tilt unit. In outdoor applications, the pan/tilt mechanism and the housing containing the camera/lens must be designed to withstand wind loading, precipitation, dust, dirt, and all types of vandalism.

In an outdoor application there are two options: 

(1) the lens and camera can be enclosed in an environmentally shielded housing and mounted on an environmental outdoor pan/tilt mechanism or

(2) the lens, camera, and indoor pan/tilt mechanism can be installed in an environmentally enclosed housing or dome. The advantages and disadvantages of these two techniques are discussed.

Complete integrated video camera/lens/pan/tilt/ housing systems have been introduced, in which all these parts are integrated into a custom housing or dome. Typical systems are discussed in the following sections. In a parking lot or building exterior, pan/tilt lens/ camera systems are mounted on a pedestal or on a wall or ceiling, with mounting brackets. For covert applications, all pan/tilt and zoom camera/lens hardware is hidden behind a wall or ceiling. The transmission of the video signal and the control of pan/tilt mechanism movement and lens function are accomplished through separate video and control cables or through a multiplexed communication channel where the video signal and the controls are combined on a single coaxial cable or UTP, thereby eliminating additional wiring.

Scene coverage required

The intelligence the security guard obtains from the monitor picture is only as good as the information the camera/ lens combination sees. It is therefore important to determine the viewing requirements of each camera/lens and select the optimum combination for transmitting maximum intelligence to the operator. The video system designer must decide whether a camera will be mounted on a fixed mount (pointed in only one direction), or on a pan, tilt, or pan/tilt platform so that the camera can be pointed in any direction.

A good analogy is the seeing ability of a human: when we look in a single direction, we see all of the activity in that direction all of the time. When we move our eyes or head in another direction within a large FOV, we cannot see the entire scene at one time, and therefore cannot see all of the activity in the entire FOV that our eyes can see. The 3G Wi-Fi Camera in essence time shares the viewing of the scene, spending a fraction of time looking at any particular portion of the total scene area. In order to analyze this viewing requirement, video applications are divided into three types: point, area, and volume.

Point Scenes

A typical security surveillance point scene might be a supermarket checkout line, where the information of interest is the merchandise being rung up, the amount displayed on the cash register, the cashier, and the customer; or the scene might be a bank teller station, where the crucial intelligence is the identity of the customer. In such scenes, all of the activity occurs in a relatively small part of the FOV. Although a single camera with an FFL lens may be satisfactory, a better solution might be a fixed two-lens, one-camera system, with one lens viewing the amount rung up on the cash register and the other viewing the cashier, customer, and merchandise. Another solution is a zoom lens with some panning and tilting motion. This would be necessary in a jewelry or department store where the counter area is viewed with a wide-angle lens and a small piece of jewelry is viewed with a narrow-angle lens. The pan/tilt is necessary with a zoom lens because the high-magnification (telephoto) position results in a very small FOV, so the camera must be pointed at the exact center of the target. 

In the wide-field scene, the article of interest is not normally centered in the FOV. In this situation, the operator must redirect the camera/lens combination via the pan/tilt control to center the object of interest and make it observable in the high-magnification position

More information at http://www.jimilab.com/tutorial/ .