A document camera is constructed from a number of component parts which can vary depending on which document camera model you are using. To help people better understand how a document camera is constructed, Document Camera Experts USA has put together the following section with each document camera part listed and a short description explaining each one.
The document camera’s arm or column
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Document cameras usually have one of two kinds of column or arm which functions to connect the document camera’s camera to its base stand. Gooseneck columns and rigid columns are generally used in modern digital presenters.
Gooseneck document camera arms
Document cameras that utilize a gooseneck arm have a flexible column which connects the document camera’s head to its base stand. The gooseneck arm also contains any cables necessary to attach the two document camera parts. Document cameras that have a gooseneck column are extremely maneuverable since these types of document camera arms can be bent and flexed to position the document camera’s head over the subject material being viewed.
Although the document camera’s gooseneck arm is flexible, it will also stay in one position once it has been moved into place. This makes gooseneck document camera arms a great way to show images taken through microscopes because the document camera’s head can be positioned directly over the microscope’s eye piece.
Rigid document camera columns
If a document camera has a rigid column, it means that the arm connecting the document camera’s head to its base stand is fixed and rigid, with any necessary cables running through the column. The rigid document camera arm can either be a fixed length, or it could be an extendable telescopic style one. Rigid document camera columns are generally attached to the document camera’s base stand using a hinge assembly. This increases portability by allowing the document camera’s camera and column to be folded down while it is being transported, or alternately the column can be lowered if necessary to enable better viewing of the subject material on the document camera’s base.
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The base stand of the document camera
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The base of a document camera serves two main functions. The first is for the stability of the document camera – a sturdy base means that the document camera will not fall over easily which is important because this could damage the document camera’s camera lens. Secondly, a document camera’s base holds the main power, control panels, input and output connections, processing circuitry and the base light. Occasionally, the document camera’s camera may actually be housed in the document camera base. This is particularly the case in WolfVision document camera models.
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The document camera’s base lights or light box
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If a document camera has a base light fitted, it means that the subject material being displayed by the document camera can be illuminated from behind. This is important when displaying material such as transparencies. Document camera light boxes can vary in their size from 127mm by 100mm up to an A4 size (approximately 297mm by 210mm). The lighting provided in a document camera’s light box is usually from two cold cathode fluorescent lamps which are found on either side of the lighting assembly. This allows light to be spread out evenly across the whole surface.
Where light boxes are not integrated into the document camera itself, optional accessory light boxes can often be purchased for select document camera models.
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The actual camera of the document camera
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Document camera image sensors
The integral part of any digital presenter or visualizer is its camera. The camera will determine what is shown by the document camera, and the level of image quality that the document camera is able to display. The camera unit will usually consist of one of two types to image sensor - either a CCD or CMOS Active Pixel Sensor. Progressive Scan CCD technology is also used in certain document camera models.
The lens array found on the front of the document camera’s image sensor is also a key aspect which contributes to the quality of the image displayed, in combination with the resolution of the document camera’s image sensor itself. In any document camera, these two factors can provide the difference between a good document camera picture and a great document camera picture.
Document camera lenses
The majority of document camera models available on the market will be supplied with a motorized zoom lens which makes selecting the correct view of the subject material an easy task.
Desktop document cameras may also come fitted with a close up zoom camera lens, which will depend on the construction and depth of field of the camera’s original lens. A close up document camera lens means that the camera can focus and magnify the subject material from a short distance away – for example, the distance between the camera and the viewing stage. When the document camera is used to view material that is far way by rotating the camera housing away from the stage, this close up document camera lens is unnecessary.
There are two types of fixings which are commonly used to attach these close up lenses to the document camera. The lens can be screwed on, in much the same way as it would be on a regular SLR camera lens filter, or it could be housed in a narrow frame and attached to the document camera head using a hinge mechanism. The hinge allows the close up lens to be flipped down over the main document camera lens when close up viewing is required, and flipped up to remove the use of the close up lens when distance viewing is necessary.
Document camera heads may also contain a wireless remote control receiver which will allow maximum visibility for the reception of signals transmitted from the handheld document camera remote control.
Camera movement
The document camera’s camera unit is usually found in a housing which is fixed in a way that will allow the camera to move about on its axis. The design of the specific document camera will decide the actual degree of movement available to the camera. With a gooseneck style of document camera column, the unit’s camera housing is normally fixed and is not able to move very much, but the user is able to position the camera using the flexible gooseneck itself.
Digital presenter models with rigid columns will most often have their cameras housed in a unit which is attached to an assembly that allows the document camera’s camera to move vertically to approximately 90 degrees to either side of the position where the camera is looking straight down. This feature means that the document camera can be pointed both forwards and backwards from the viewing stage. Unless compensated for, the image captured by the document camera when the camera is pointed rearwards from the stage will be upside down, although some document camera models will provide features which compensate for this problem. When looking away from the operator the image will be the correct way up.
Top mirror viewing digital presenters
Document camera models which come with a top mirror viewing function will have their camera housed either in the base of the unit (which is the case with Wolf Vision document cameras) or in the document camera’s column. Wolf Vision document cameras have a motorized top mirror assembly in their two leading desktop document camera models which also gives these document cameras an image scrolling effect.
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Ceiling mounted document cameras
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Ceiling mounted document cameras are an unusual type of document camera and so they have features which are not typical to other document camera types. Ceiling mounted document cameras will have a camera, motorized zoom lens and connectivity options just like any other type of document camera, but they will also include ceiling mounting capability and can be operated by remote control. Where necessary, the housings of ceiling mounted document cameras will be plenum rated for fire resistance in ceiling voids.
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The document camera’s control panel
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Document camera control panels are purposefully positioned to provide ease of access to presenters, and are located in such a position that the presenter’s arm will not get in the way of the document camera while they are using it.
Desktop document cameras models will frequently have a control panel that is positioned either on the camera’s head or at the front of the document camera’s base stage.
The actual size of the document camera’s control panel and its complexity will often depend on the types of functions that the document camera can perform. Most document camera control panels utilize pushable buttons, but some will also include "jog shuffle" type controls. All document camera control panels are specifically designed to be easy to use, meaning that someone using the document camera for the first time can operate the device within a very short time frame.
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The document camera’s input and output panel
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A document camera’s input and output connections panel can usually be found at the rear or at the side of the document camera’s base stand. The exception to this rule is for USB-only connected document camera models. The size and functionality of the input and output panels will depend on what features the document camera offers. Document camera input/output panels may only have a single connector, or they could provide a whole suite of connectivity options to allow connectivity with type and resolution of display.
The types of connections that you will most often find on a document camera’s inout and output panel are as follows:
- D-sub 15 pin VGA
- S-Video (4 pin Mini DIN)
- Composite Video (RCA/Phono)
- BNC
DVI connection is becoming increasingly more common in document cameras, and High-Definition multimedia Interface (HDMI) is offered on Wolf Vision document camera models.
Document camera audio connectivity is provided by either mini jack or RCA/Phono connectors. Connectivity to a PC is provided almost exclusively by USB 1.0/1.1 (12 Mbits/second) or USB 2.0 (up to 480 Mbits/second). Network Connection 8P8C (commonly referred to as RJ-45) connections are also available for PC networking connectivity in document camera models made by Wolf Vision.
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Overhead document camera lights
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Often document cameras will come with built in lights which are used to illuminate the subject matter. These document camera lights can vary in their number, output power, size and type. For example, several document camera manufacturers have chosen to use LED technology in their document cameras because LEDs provide excellent color temperature, lifespan and intensity and are cost effective. Other document camera manufacturers use CCFL (cold cathode fluorescent) lights, or even standard fluorescent or halogen lamps which are equally as efficient.
Document camera lighting positions
A document camera’s lighting fixtures can be positioned in a variety of ways. Some document cameras have lights mounted on additional separate columns which are smaller and attached to the side of the document camera’s base. Other document cameras have their lights positioned at the point on the main column where the hinge is located, and some document cameras have their lights built into the actual camera head.
Document camera lighting adjustments
Very often the lighting provided with a document camera is specifically designed to allow directional control of the document camera’s light, which means that the amount of light reaching the document camera from the subject can be varied. This directional light adjustment means that optimal illumination of the subject matter is possible by gradually rotating the light unit and the angle of adjustment of the arms that the light unit is mounted to. This can reduce problems such as hot spots or white outs which can reduce the quality of the projected image.
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Projector integrated document cameras
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There are currently two models of document camera available to consumers which combine both a projector and document camera in one unit. Both of these projector document camera models are made by Toshiba.
These two in one document camera projectors have the document camera attached to the side of the projector’s body. The camera uses a 3 Megapixel CMOS image sensor and 8x digital zoom capabilities. Illumination of the document camera’s subject matter is provided by LEDs. The projector part of the unit is an LCD projector with a brightness output of 2000 ANSI Lumens. The projector can project images from the document camera in an XGA resolution of 1024 by 768 pixels.
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