Machine Design

Live! Exposed! And on the Web!

It was late afternoon and the action in front of the Webcam was getting pretty steamy. "Voyeurs" from across the country would type in something they'd like see, then wait in anticipation as the three on-screen performers carried out their wishes.

The demonstration set up by Opto 22 lets viewers control a light bulb, spinning disk, and voltmeter by clicking buttons on their browsers. Commands from viewers travel over the Internet to the Ethernet I/O module, visible in the top left of the scene, which controls the performers.

The $150 QuickCam Pro is an example of an inexpensive USB video camera. From Logitech Inc. of Fremont, Calif., it shoots images at a 640 480 (VGA) resolution. A microphone and software for video editing, photo enhancement and digital surveillance are included.

Billed as the first complete digital-imaging module, the PCM2112 combines a lens/shutter assembly with a 1,280 1,024 CMOS color-image sensor. The sensor is exactly aligned with the optical axis for uniform image focus. An attached ribbon cable controls shutter release and on-the-fly programming to select between resolution, frame rate and bit width. The module can also zoom, pan, tilt, flip, and mirror. It puts out a 10-bit color image at up to 102 fps and uses an architecture that makes it possible to migrate to cameras with higher pixel densities. The developer, PixelCam Inc. of Campbell, Calif., says the $69.80 module can serve as the basis for a variety of video applications.

Internet-based monitoring and surveillance is the target for the Inetcam VTS 8500 Color Video Transmission System. From Inetcam Inc. in San Diego, this $429 system includes two color video cameras and a four-port video switcher that handles four cameras. The switcher hooks into a host computer via a serial connection. (The host needs a video-capture card.) Cameras can sit up to 500 ft from the switcher. Bundled-in software sets up HTML and Java files to serve videos from Web servers. Server side controls include transmission parameters such as window size, frame speed, and compression rate. No plug-ins are required to view the video, just small Java modules. Viewers can adjust image brightness and contrast.

The freebie of the week? Yet another case of Internet porn? Nope. The performers were a light bulb, a spinning disk, and a voltmeter. They sat inside a box in front of a Webcam set up by controls vendor Opto 22 to dramatize potential applications of Ethernet I/O. Things were getting steamy because a viewer somewhere had clicked a browser button that turned on the light bulb. Observers could monitor temperature in the display box from thermometer readings fed to an I/O rack and out to the Internet. Though the Opto 22 demonstration in Temecula, Calif., is modest, it looks like a harbinger of industrial tools. Webcams are migrating out of the novelty category and into mainstream industrial practice. Growing Internet bandwidth makes them practical alternatives to closed-circuit TV, and opens up wholly new application areas as well.

For example, Opto 22 says it is working with companies devising Webcam systems for school building security. Sensors that notice a door opening, or other potentially interesting events, will trigger a camera that photographs whoever is going in or out. The image feeds over a net and is available to security personnel through an ordinary browser.

Machinery is another candidate for remote monitoring via Webcam. Among the first applications foreseen in this area are unmanned generator sets. Backup power systems for isolated areas often have no human operator nearby. Webcams are envisioned as a way of ensuring there are no animals, debris, or bystanders in the way before powering up the generator. There are similar ideas afloat for production equipment and tools.

The simplest Webcams employ USB connections back to either computers or network appliances such as a router, hub, or concentrator. Also called plug-and-play cameras, they are inexpensive, often retailing for about $200 or less, and available from a variety of suppliers. These devices boast an image quality good enough for general-purpose work. (The Opto 22 site uses one of these.) Typical resolution is 640 480 pixels at most, though they can be set up to image at lower resolutions to reduce bandwidth demands. Typical frame rates are in the one to three frames/sec range.

Cameras targeting more demanding uses provide much higher resolution. Those aimed at machine vision or scientific microscopy, for example, can record images at 1,300 1,030 densities or more with 10-bit color representation. They can also put out 12 frames/sec at this resolution.

An alternative to Webcams is to hook an ordinary camcorder into a video capture device. Capture devices digitize NTSC video into MPEG images with resolutions of about 700 575 pixels. Images go to a host or server via ISA or PCI slots.

Network cameras are a refinement. They connect directly to networks via Ethernet connections. Though more expensive, they eliminate the need for a separate computer to host the camera. Similarly, network-video-capture devices are stand-alone electronic boxes that accept camcorder signals and perform similar functions.

Raw images from cameras typically get compressed before being passed to a server. Simple USB cameras depend on software running on the PC or host for compression. Network capture devices generally have their own processor, and one of its tasks is shrinking images.

Image size and frame rate (or image update rate) are trade-offs. To accommodate users with modem/dial-up connections, Webcam operators may deliver relatively low-resolution (and relatively small) images of about 160 120. This lets slow connections update at a rate of about once per second. It's possible to deliver images over the Web at resolutions as high as that of the camera imager itself, but at slower update rates.

There are two methods of getting images to show up in a Web page, one slow, the other fast. Hobbyists Webcasting their aquarium and similar scenes generally use client-pull broadcasting. This sends the last image shot by the camera to the ISP hosting the site. Viewers down-loading the page see a still image, the one that happened to be cached when the download began. To update the image, they hit the browser's reload button. Alternatively, an HTML tag or Java applet on the page could reload the image automatically at periodic intervals.

The main benefit of client-pull is that it works well with browsers on slow connections. The other method, server push, may not. But it is required when real-time video is the goal. In server push, HTML code in the page tells the browser to expect a series of images. The server hosting the camera sends data any time it wants to.

For example, suppose the server software is set to transmit two frames per second onto the Web. Provided their Net connection is fast enough, viewers should see two frames per second appear in their browser. However, sufficiently powerful server software can send video at changing frame rates. The classic example is that of a program which determines if the current video image resembles the previous one. It only sends a frame when the signal changes appreciably. There is an obvious conservation of bandwidth. Clever techniques such as this can make near real-time video practical for viewers on relatively slow hook ups.

Controls vendors such as Opto 22 plan to tie a variety of peripheral devices more closely into industrial I/O modules. Webcams are one of the devices on the list. Eventually, USB cameras will plug directly into an industrial Ethernet I/O module to connect with the Internet.

Another development, XML data standards, is expected to indirectly make Webcams easier to deploy for industrial use. Specifically, XML may slash the effort needed to define Web pages associated with industrial monitoring.

XML defines data elements on a Web page and in business documents. It uses tags analogous to those in HTML. The difference is that HTML tags define how elements are displayed, while XML tags define what the elements contain.

Moreover, the person developing the Web page defines the meaning of specific XML tags. Specifying XML tags for entities such as pressure, temperature, force, and so forth is critical for industrial use. For example, pages containing Webcam images may well contain XML-tagged fields for time, view, magnification, and other entities associated with monitoring scenes in real time.

This sort of identification could let Web pages function like database records. In so doing, it may eliminate some complexity now associated with data logging and monitoring.

The many views of Webcam technology
The least-expensive Webcam systems employ cameras that send images to a host via a USB interface. The host may cache camera data and serves as either an Ethernet port or a vehicle for dial-up connections. (Hobbyists are the main users of the latter case. To put out images over the Internet, they must arrange with their ISP to get a static IP address, one that doesn't change every time they dial in.)

Ordinary camcorders can serve as Webcams through use of special video capture equipment. Video-capture devices accept NTSC video and audio from camcorders and translate it into MPEG format for the Net. The most recent generation of these devices double as Web servers, eliminating the need for separate hosts. Some accept signals from multiple camcorders. Built-in Ethernet interfaces let them host video for use over intranets or the Internet.

Network video cameras combine Web-server and camera functions in one housing. Because network cameras do not use the relatively slow

USB connection for transmitting images, they may offer options for faster frame rates and images with more resolution than is possible with less-expensive equipment.

Streaming video goes panoramic

Those who viewed the recent G.O.P. National Convention and this week's Democratic Convention on selected Web sites got a chance to see in action one of the more novel devices now creating video on Web pages. Called the Be Here 360lens and created by Be Here Corp. in Cupertino, Calif., it captures scenes in a full 360° around itself. It does so by means of a circular mirror that reflects images down a thin stem and into the lens of an attached camera.

The image that results is donut shaped. Special software turns it into a strip that is compressed and sent over the Web. Typical viewers see only a small portion of the strip, but can pan a window across it or zoom in and out using a mouse. Compression degrades the picture quality somewhat compared to other on-line videos, a compromise aimed at accommodating viewers on dial-up connections.

Users frequently combine the Be Here 360lens with a high-res digital video camera such as the DVC-1300-C from DVC Co., Austin, Tex. The more typical application for these 1,300 1,030-pixel devices is in machine vision or inspecting integrated circuits through a microscope (left). The set up provides 10-bit RGB images at 12 frames/sec, and works at low — 0.001 ft-candle — light levels via on-CCD integration.

Where to find information
Be Here Corp.
Supplies Web broadcasting systems centered around the 360° Be Here lens.
Darim Vision Corp.
Supplier of stand-alone systems that connect camcorders to an Ethernet network.
Supplier of high-res digital video cameras, generally for scientific and industrial use.
Inetcam Inc.
Supplier of digital video systems targeting surveillance applications. Logitech Corp.
Supplier of USB video cameras.
Opto 22
Supplier of industrial I/O with Ethernet connections.
PixelCam Inc.
Supplier of OEM imaging modules for digital video.
Webcam Store
One-stop shop for webcam hardware and software.

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