Document camera

A Visualizer ( Document Camera also ) is a video camera for pictures with the light from a light source document or article in a presentation. It can record any kind of material ( books, photos, three-dimensional objects, etc.) quickly and easily and provides a high resolution image for projectors, interactive whiteboards or videoconferencing systems. This flexible presentation device may be considered as a further development of the episcope or the overhead projector.

• 4.1 Table models ( Desktop Visualizer )
• 4.2 ceilings models ( Ceiling Visualizer )

General operation and applications

The Visualizer converts the image of the original into an analog or digital video signal, which is then fed to a separate video projector or monitor. The camera may be either before the mirror may be mounted in place of the projection lens, or on a supporting arm. There are other designs that can be hung directly on the ceiling. The document is either placed on a glass plate and illuminated from below or placed under the camera and illuminated from the side lamps. Externally similar to the visualizer then a flatbed scanner or a Repro Stand out of the Photography, depending on where the camera is mounted.

The predominant part of a Visualizer is usually attached to an arm and is used in conjunction with projectors in classrooms or during presentations. Visualizer very often used as a substitute for overhead projectors. Some visualizer can also be used in conjunction with a microscope.

Visualizers are actually more closely related with scanners than with projectors, as they have no means for an active projection and it must be connected to an optical reproducing device.

Historically

The first visualizer was developed to satisfy the growing demands for projection and presentation of original documents, plans, drawings and objects, instead of being compelled to copy these objects on a slide in order to integrate them into a presentation using overhead projector.

With the further spread of computers and projectors in meeting rooms Also, demand for the replacement of the overhead projector ( OHP ) to give the presenters more opportunities away from the usual presentation programs such as PowerPoint. In the early days this was very often an easy way to spontaneously integrate the ongoing presence of overhead transparencies or individual slides in the lectures without having to install additional devices. In addition, however, the lecturer had additional opportunities and could, for example, visualize a book spontaneously and directly.

The first steps and prototypes were mostly simple video cameras mounted on a copy stand ( from the professional photography ) and were also equipped with lights to ensure independence of the environmental conditions ( especially in a darkened room so that the visibility of the projected image and the contrast was guaranteed the CRT projectors ). The then prevailing video technology of the cameras was a significant factor determining the resolution of the system.

Visualizers have frequently from developments in other sectors benefited, some of which also enabled quantum leaps in the field of Visualizertechnologie. A good example here is the camera technology used. After the original models very often have simple black and white cameras, the use of color cameras was a real milestone, what the presentation quality were concerned.

The long -time dominant video camera technology was in the late 1990s for the first time accompanied by progressive scan cameras (PS ) cameras. Compared to the Interlace method by a video camera ( reading of fields ) always indicates the entire image is read in a PS camera, which made ​​itself felt in the camera resolution. Originally, however, had in the frame rate ( refresh rate, that is how many images are displayed per second) swabs are taken into account, since neither image sensors nor the motherboard used were able to handle the increased data volume.

Nowadays PS cameras Video cameras have largely eliminated from the market and the initial difficulties in using PS technology are virtually eliminated. Many Visualizer available on the market can at least spend 20 fps (frames per second), high-end models are able to represent 30 fps in a variety of resolutions and aspect ratios easily.

Technology

The design and specification of a Visualizer caused by the mix and the use of various technologies. These are primarily the module optics, camera, a lighting system and a motherboard with the included firmware (software) for the quality of the captured image. The whole is realized by a wide variety of mechanical structures of the individual manufacturers.

Optics

The look is one of the most critical components when it comes to image quality. Depending on the price range of the device simple lens systems to highly complex optical systems are used, which differ markedly in quality and size. Optics located in the another important component of the iris or the shutter. The iris controls and regulates the amount of light through the lens to the image sensor.

When an object to be imaged on the image sensor, so there is one point where a lens is in focus. There are, however, before and after the object is still an area that is sharp enough for the human eye, the so-called depth of field. It depends on several factors, but mainly from the aperture ( iris or iris ). The smaller the aperture, the greater the depth of field ( and vice versa).

Camera

Today's most commonly used progressive-scan cameras use either CCDs or CMOS sensors. The general advantage over video cameras is the much higher resolution, as opposed to interlaced scan ( interlaced method ) at a PS camera, the full image is read and not just half-images are superimposed on each other at different times.

Basically, image sensors can only provide monochrome images. With a 1-chip color camera such information can be obtained through the use of color filters on each pixel. With 1- chip cameras, the so-called Bayer filter is very common, here red, green and blue filters are arranged in a specific pattern. The number of green pixels is twice as large as that of blue and red, so that the higher sensitivity and resolution of the human eye is modeled to green light. Will get a color image a wide variety of algorithms used to interpolate the missing color information. However, a lower resolution of the camera must be taken into account.

A further possibility for the production of color images is the use of a prism splits the white light into its red, green and blue components, and directs to the sensor of the respective color. This sophisticated camera technology is used in 3- chip cameras and enables excellent color reproduction at very high resolutions.

Modern camera systems which are used in Visualizer, are able to provide high-resolution color images at 30 frames per second. The resolution may be measured in a 3- chip camera with up to 1500 lines. In addition, the commonly used today page formats of 4:3, 16:9 and 16:10 are easily adapted or adjusted to the existing display.

Lighting

Lighting is an essential part of a Visualizer. In order to ensure good color rendering, the lighting system has to illuminate the reception area as homogeneous as possible. The higher the light intensity, the more independent it is from ambient light. In addition, powerful lighting systems a small aperture sufficient and this in turn has a significant influence on the depth of the Visualizer (the smaller the aperture, the greater the depth of field). The better the lighting is, the more light will arrive on the camera sensor and the less a disturbing image noise is noticeable.

Various Visualizer models integrated into the lighting additional functionality, such as a synchronized field of light at all times clearly indicates to the operator that detail is being shown to the audience.

Motherboard and firmware

Modern camera systems present a great challenge for the motherboard dar. Increasingly large resolutions and high refresh rates generate large amounts of data that must be processed in real time. The motherboard and running thereon image processing have great influence on the eventual image quality.

Good Visualizers have a variety of sophisticated automated systems on board that will make the user's life as easy as possible. A permanent AF detected, for example template changes automatically and adjusts the focus settings, without the assistance of the lecturer, in fractions of seconds. Other important automatic features include the Auto Iris, Auto Exposure, Auto White Balance and Automatic Gain Control.

As already mentioned, Visualizer need an image playback device, to show the information to the public. Modern motherboards have a variety of connectors to ensure flexibility in the application. In addition to HDMI, DVI, VGA and video ports for connecting to displays ( projectors, monitors, and video conferencing systems ) you can also find a variety of computer interfaces in order to accomplish a connection to the computer, the interactive whiteboard or at room control systems. These are mainly USB, Network ( LAN) and serial interfaces.

In addition, external PCs or laptops can be connected to the Visualizer to easily switch between a PowerPoint presentation, or live demonstration. Different models can deal with external storage media and play files directly from a USB stick or save snapshots during the presentation of it.

Some Visualizer will allow upgrade your firmware and can be equipped with new functions.

Designs

There are some types of Visualizers, generally can be divided into two groups. Some are table models in various forms, and the other group are the so-called Deckenvisualizer.

Table models ( Desktop Visualizer )

Table models are classic Visualizer, which allow a similar work, such as on an overhead projector. The switch is easy and many users will appreciate the extra flexibility in terms of usable objects, but without having to take major technical hurdles in buying. The devices can also be used mobile, that is, a device can be used as needed in different rooms without the need for a large installation costs.

Visualizer with flexible arm ( gooseneck ) Lumens

Visualizer from Samsung

Visualizer Wolf Vision

Ceiling models ( Ceiling Visualizer )

Ceiling models are an evolution of table models and give the user some additional degrees of freedom. The objects to be visualized may be substantially greater, for example. Deckenvisualizer allow a completely natural feel, because the normal meeting table is converted to the work surface by pressing a key. The view of the speaker to the audience and vice versa is not adjusted by a technical tool, but the technology that is designed to support, makes it quietly in the background. This aspect is particularly useful for telepresence systems ( high- end video conferencing ) to support, since the illusion is to be produced, that the call participants sit at the same table in the same room.

Ceiling models can be also retracts completely into the ceiling, should the design of the space in the foreground.

Applications

With a Visualizer can theoretically all be represented. Most objects are simply placed under the camera, the camera captures the image and outputs this live image, for example means projector. Different Types of Visualizers allow for great flexibility in terms of placement of objects. Thus, larger objects, for example, simply be placed before it and the camera and the Visualizer can be easily rotated. Or the Visualizer is equal mounted on the ceiling and allows a completely natural feel without that technology is perceived at all.

Typical applications for Visualizers are: training, meetings, conferences, seminars, product launches, presentations of evidence in courtrooms, various medical applications ( telemedicine, telepathology, x-rays, etc.), video conferencing and telepresence ( using the Visualizer as a document camera ).