Design News is part of the Informa Markets Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them. Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Sitemap


Articles from 2007 In April


Boeing Dreamliner Drives Carbon Fiber Composites

Boeing Dreamliner Drives Carbon Fiber Composites

One of outcomes of the drive to reduce fuel consumption will be a major drive to composites. Boeing’s 787 Dreamliner will improve fuel efficiency 20 percent through use of composites in half of its structure. All of the material is coming, at least for now, from Toray Industries, the world’s largest supplier of PAN-based carbon fiber. Toray says demand for the material is growing at a 15 per cent annual rate, with much of the immediate push coming from the Boeing 787 Dreamliner. But Toray says a major demand developing from auto producers, which are already experimenting with high-tech thermoplastic composites. The carbon fiber matrices will also be used more in CNG tanks. Prices of the materials are soaring, and there have been reports of supply constraints. Toray is spending close to $1 billion now to boost capacity.

Gadget Freak Case 101: In at Whatever, Out at 12:00

April 30, 2007
Latest Gadget Freak
In at Whatever, Out at 12:00
Case File #101
John Linstrom's portable tape player made quick roadkill of batteries. The car's 12V system would eliminate the carnage, but the range of voltage at the lighter socket was too wide to power the tape player directly. This Buck/Boost voltage regulator solved that problem. Get the Build Instructions
Give us your feedback on this Gadget Freak
ADVERTISEMENT
In the News:
Beer Tossing Refrigerator - Update
The press John Cornwell is getting on his refrigerator, which will allow you to grab a beer without ever leaving your couch, is inspiring the inventor to produce a limited number of beer-launching refrigerators. Full Story
Sensors Play a Key Role in Developing New Toys
The initial applications that drive sensor companies to invest in new market technology research are frequently in automotive, medical, industrial or military/aerospace. However, once new sensors exist, sometimes it is all fun and games. Full Story
News from the Hannover Fair
Design News was in Germany along with 6,000 exhibitors from 60 countries for the Hannover Technology Fair. Innovations include a new ball bearing family and fluidic muscles in robotics. Videos Available. Full Story
FIRST Robotics: Video Coverage from the Competition Floor
This year's FIRST Robotics Competition encouraged students to use advanced tools and machines to design and build the best robot for the challenge. Design News takes a behind-the-scenes look at what it takes to be an FRC contender. Watch Now
ADVERTISEMENT


Sponsored Technology Content

RAQ's - Breadboarding With Surface Mount ICs In partnership with ADI
How do you build breadboards with tiny surface mount (SM) ICs? Contributing writer, James Bryant answers this and relates another strange but true story from the call logs of Analog Devices. Read More
ADVERTISEMENT
PAST GADGET FREAKS

William Noticed a Vibration
The fluid in William Grill's Seismic Detector reveals subtle vibrations. The detector is built around a laser pointer, hobby-type mirrors, a PIN photdiode and a regulator and amplifier.

Bob Had a Problem with the Thermal Management
Bob Wilson's office was freezing, but building maintenance wouldn't help him. So, he devised this gadget to track his office temperature.

Bob Solved His Chip Problem
Bob Neidorff's souped-up shop vac gadget cleans up after wood chip messes even a woodchuck would shun.
Build Instructions >> Build Instructions >> Build Instructions >>
ADVERTISEMENT

In at Whatever, Out at 12:00
Beer Tossing Refrigerator - Update
Sensors Play a Key Role in Developing New Toys
News from the Hannover Fair
FIRST Robotics: Video Coverage from the Competition Floor
Past Gadget Freaks
 Contact Us

Check out our new Gadget Freak blog! We're looking for your feedback - humor, sarcasm, opinion and rebuttal are strongly encouraged. Read More
Calling All Gadget Freaks...
Do you have what it takes to be the next Gadget Freak?
E-mail a description of your project to us. If your project is selected, we'll feature it in an upcoming edition of the magazine and send you a check for $500.
Download the entry form
elizabeth.taurasi@reedbusiness.com?Subject=Gadget Freak EntryE-mail us
Gadget Freak RSS


Products/Services
Companies

        Fine Print
You are receiving this e-mail because you have requested either a newsletter or a magazine from Reed Business Information.
Subscribe to Design News' e-mail newsletters | Unsubscribe from the Gadget Freak E-Newsletter | Update Your Profile - cancel or change your newsletter subscriptions, change your e-mail address or profile | Free Print Subscription | Privacy Policy
QUESTIONS? If you have questions or need further assistance, please contact our Customer support staff
Reed Business Information 225 Wyman St. Waltham, MA 02451 | Fax: 303-265-2983

STAFF: Editor-in-Chief: John Dodge | Managing Editor: Liz Taurasi | Web Producer: Arash Hadipanah | Web Editor: Regina Lynch
PRIVACY MANAGER: Reed Business Information 2000 Clearwater Drive Oak Brook, IL 60523 | Fax: 630-288-8394
Copyright 2007, Reed Business Information, a division of Reed Elsevier Inc.
Could I-580 overpass collapse been averted?

Could I-580 overpass collapse been averted?

The Contra Costa Times has a pretty good video of last night's I-580 overpass collapse that is sure to gridlock traffic in San Francisco that on a normal day is tough to navigate. In a terse one sentence advisory, the I-580 traffics condition report urges commuters to seek alternate routes. The collapse caused an inferno from an exploding gasoline truck that failed to negotiate a curve. The disaster is reminscent of the Big Dig ceiling collapse in Boston last summer that tied up traffic for months.

Should a highway be able to withstand such an unusual accident? Indeed, the engineering in the rebuilding of I-880 in Oakland from the 1989 earthquake measuring 7.1 on the Richter Scale factored in future earthquakes. But how often does a truck explode in California? Comparatively, quite a bit. I was in San Francisco when a gasoline truck exploded inside the Caldecott Tunnel on April 7, 1982, killing seven. In 2001, a truck driver rammed the California state Capital Building with a truck loaded with 65,000 cans of evaporated milk that caught fire. 

So funky things like tanker explosions inevitably occur on California highways and byways. Should (or could) a highway be able withstand such an inferno? Hardly. Though, I am not a civil engineer, that would would be tantamount to making them withstand a bombing. 
  

      

Corn Ethanol is Dead, but Cellulosic Ethanol has Promise

Corn Ethanol is Dead, but Cellulosic Ethanol has Promise

I have already shared my opinion that corn-based ethanol is idiotic (see Let the Sun Set on Corn-Based Ethanol), and I have shown how the stock market punishes corn ethanol plays (see Corn-Based Ethanol: The Free Market Speaks). I even illustrated Brazil’s excellent progress on sugar-based ethanol, which represents the “correct” model for distillation of this renewable fuel (see US and Brazil Plan Global Ethanol Market).

In response to my ethanol rants, a reader with the handle iolight posted the following comment, “I don’t understand why you are essentially discounting the new studies… Improvements in processing are working; so, corn ethanol is becoming more and more efficient while buying us time… Your pessimism sounds unsubstantiated.”

To prove that I am not a complete ethanol ninny, I want to point out that a few pilot cellulosic ethanol plants are now coming on-line as highlighted in Technology Review, “Will Cellulosic Ethanol Take Off?”, and PE Magazine, “States Experiment With Next-Generation Ethanol”. Cellulose arises mainly from agricultural waste; the non-food bi-products such as stalks and corn cobs. My beef with corn ethanol is that it takes about the same energy to make the stuff as the fuel itself contains. However, if extra energy can be extracted from agricultural waste, ethanol production may become an energy-positive prospect. If cellulose material could be economically converted to ethanol, my opinion of this fuel would certainly be less pessimistic.

The good news is that Iogen Corporation already has an operating cellulosic ethanol pilot plant. Celunol broke ground on another such facility in February. Several other companies have plants in the works. The bad news is that despite these promising toe-holds, cellulosic ethanol is still difficult to create, requiring a multi-step process that is more expensive than its corn-based rival. What is needed is massive investment in technology to push cellulose ethanol past the energy break-even point and to drive the price down below corn ethanol.

When addressing questions of energy independence and sustainability on April 26, several debating Democrats brought up ethanol and the need for Apollo-Program-scale investment in energy technology. Perhaps the politicians will put the pieces together and funnel funding toward cellulose ethanol, which in the eyes of this blogger has bright prospects to begin moving the U.S. towards independence from foreign oil.

Ecological Camping with Low-Power LED Lanterns

Even camping lanterns are going green. Rather than burning camp fuel, camping lanterns from Favour Light Enterprise Ltd. of Dongguan, China, illuminates campsites with low-power LEDs powered by batteries. Favour, one of the largest flashlight makers, employs Cree’s XLamp XR-E power LEDs for camping lanterns and numerous flashlight models. The white Cree XR-E LEDs produce typical luminous flux of 80 lumens at 350 mA, yielding 70 lumens per watt.

Nitro Methane Motorcycle Coded for Speed with Prowork Digital Controller

Salakazi Racing’s KTM nitro methane motorcycle/dragster does the quarter mile in 6.7 sec, with a terminal velocity of 196 mph. One key for reaching these speeds is an automatic three-disc, four-stage clutch fitted with a Proworx digital controller. That controller is pre-programmed for optimal speed given the racing conditions it encounters. Inside this clutch, there are a few tiny but critical devices. Among them are a pair of RM22 encoders from Gloucestershire, United Kingdom-based Renishaw. The encoders are both fast and precise enough to monitor speeds up to 30,000 rpm. One monitors the position of the crankshaft in the engine, while the other measures the clutch speed. When these two values are compared, clutch slippage, traction and road conditions can be determined with high precision.

Autos Eliminate Bulbs for LEDs

White LEDs are still fairly new, but they’re now seeing use in one of most rugged applications, automotive headlights. Audi’s R8 is the first to eliminate bulbs, using LEDs for both low and high beams. Philips Lumileds designed chips that have both the brightness and durability to roll down highways for a decade or so. While LEDs are more costly than high-intensity discharge lamps, their long life and small size are a big lure for Audi. It takes less than 10 LEDs to provide 1,000 lm for each headlight.

Vision Sensing Trends

Improved processing capability, color and higher resolution create growth when it comes to vision sensing trends, according to University of Illinois Engineer Lisa Eichler.

Design News: What do you see as the main trends in vision sensing?

Lisa Eichler: The most typical thing we see is pressure for faster-smarter-smaller every year. We continue to incorporate better and better processors into the units to bring more of what we traditionally have seen as PC vision level tool capability down into the vision sensor platform. Additionally, there is certainly a demand for greater camera resolution and a broad range of camera variations to meet specific application requirements.

How important are more powerful processors?

It was just over two years ago that we were able to port PatMax, the geometric pattern recognition algorithm from PC vision, down to In-Sight because the DSPs had become powerful enough to run it. We are starting to see that trend accelerate over time. Now, we do all kinds of calibration techniques. We’re able to add a new flexible flaw detection algorithm on our DVT 5X5 vision sensors. That’s PC level vision inspection that we are talking about. To me that’s a real exciting trend because we are able to take a very high-performance algorithm and bring it down to a price point that makes it more attractive for vision sensor users.

Is color getting to be more important or easier to do at an acceptable price point?

We just introduced two (color vision sensors) and we are about to introduce another. So there will be more entry-level color choices than there have been in the past. For us, making the leap from an entry-level price point to color was pretty significant. What we are seeing on both the DVT and the In-Sight line with these two new introductions is that we have reduced the entry level price for color, while maintaining all of the vision tool capability of their monochrome counterparts.

What about Resolution? Does that tie into the transition from PC to non-PC based vision sensing?

Absolutely. When we went from having the 1024 × 768 In-Sight to introducing the 1600 × 1200 Insight, we saw that many customers immediately made use of the additional pixels. In fact, sales has started to shift more towards high resolution. We find that after having some success with entry-level vision sensors, many customers want to tackle more challenging inspections. Higher resolution allows them to do that.

How does ease-of-use enter the vision sensing picture?

I think continuing to improve ease of use is something that all of us making vision sensors will continue to focus on. That, and entry-level pricing are key to attracting new customers and opening up new applications. I think the number one deterrent to people picking up vision is the learning curve. The more we can reduce the learning curve, the more we reduce the cost of deployment and the more we grow the number of new customers and applications.

What about Connectivity?

Cognex can no longer be just a vision company. Rather, we have to be an automation company that makes vision products and connectivity is a big piece of that. For example, In-Sight now supports Modbus/TCP and EtherNet/IP and our next software release will support PROFINET communications.

When you’re a part of the control environment, connectivity ease-of-use and the time it takes to get a system connected and communicating to other devices is a really important consideration for any user and vendor.

Lisa Eichler is a University of Illinois engineer and holds an MBA from the University of Chicago. She came to Cognex with a dozen years of automation industry experience under her belt and spent two years developing the Cognex distribution channel in the Americas before becoming director of marketing for the vision sensor products.

Sensors Play a Key Role in Developing New Toys

A lot of hard work goes into developing new sensor technologies. The initial applications that drive sensor companies to invest in the research to bring new technologies to market are frequently in automotive, medical, industrial or military/aerospace. However, once new sensors exist, sometimes it is all fun and games, especially for users of some of the newest toys that take advantage of built-in sensing capabilities.

Accelerometers Get on Board

Protecting lives is serious business. Carmakers and their suppliers created the low-cost semiconductor accelerometer business based on the requirement for these sensors in airbag systems. Now that low-cost accelerometers exist, they are being applied for motion detection and stabilization in a variety of consumer electronics products from cameras to hard disk drives. The cost is low enough that new interactive games have been developed using accelerometers for motion detection. One of the more visible applications in 2006 was Nintendo’s Wii. At the 2007 Consumer Electronics Show (CES), Qmotions and Freescale Semiconductor showed attendees how to become an integral part of a snow- or skateboarding game. Qmotions-Xboard full-motion game controller uses a three-axis accelerometer developed by Freescale that measures body movement and converts it into full body action. The accelerometer’s location in an actual board allows players to really get into the game.

With the user balancing on the board, the accelerometer provides tilt feedback data regarding the motion and translates the measurements into a character in the game on either a skateboard or snowboard that tilts in the same direction. For this application, tilt recognition could have been done with a two-axis accelerometer. However, the accelerometer has a non-linear tilt output, so using the third axis for the X and Z or the Y and Z measurements provides more accurate tilt data. “It is measuring gravity, so it can use both the X and the Z for that type of rotation and when it is tilting forward, it can use the Y and the Z for getting accurate tilt measurements,” says Michelle Kelsey, marketing manager for Inertial Sensors, Freescale Semiconductor.

The accelerometer selected for the application is Freescale’s MMA7260Q, a low-g three-axis device with a g-select option that can be used to chose a range of ±1.5, ±2 ±4 or ±6g. Since Qmotions specializes in developing and marketing PC/Console-based active game technologies, the device also provides a platform for other products.

Future designs could take advantage of the accelerometer’s additional capability with a software update to the existing hardware to get more information such as shock, vibrationor fall detection. “It is pretty exciting to see how all the gaming equipment is going to be changing to be even more like a virtual reality type of input,” says Kelsey.

Alien Eyes

The innovative Roomba robotic vacuum cleaner relies on infrared (IR) sensors to detect obstacles and floor discontinuities. Four pairs of IR sensors monitor the floor to detect steps and another pair looks for walls. Using this same infrared technology, Kids Delight developed the Zig Zag Zog UFO Saucer. This toy alien avoids being captured by using three IR sensors to detect obstacles in its path and two more IR sensors in its head to warn of someone trying to reach down and bop its head — the object of the game. After being caught, the toy operates at successively higher speeds requiring even higher performance from both the sensor and detection circuitry.

Air Guitar Shirt

Not content to just go through the motions, Dr. Richard Helmer, an engineer from the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Belment, Australia, developed a textile motion sensor to capture air guitar movements and turn them into music. The sensor and custom software for interpreting gestures create a virtual instrument.

The shirt is made of highly conductive fibers. The resistance value of the fibers changes linearly with the strain and compression of stretching the fiber by various arm movements. “The sensors result in a variable voltage related to elbow bend which is digitized by electronics attached to the shirt,” says Helmer. “This is broadcast wirelessly to a computer where the signals are interpreted to deliver sounds.”

By associating a set of audio samples with different arm positions, Helmer can play a sample or part of a recorded song. For example, he can choose a particular portion with his left arm at an angle such as 45 degrees ±10 degrees and trigger the sound with his right arm as it passes 45 degrees. The system provides continuity in either “arms relaxed” or “arms flopping around a bit” modes. The same piece of music can be played in different ways providing different skill levels such as verse chorus, picking each chord or even by note. In a video clip, the inventor plays a tambourine where the sensor material is more readily observed as a set of black sleeves over the elbows.

Big Boys and Their Toys

Loading a car with the latest sensing technologies just so it can operate autonomously seems to be a fun activity, too. DARPA’s Urban Challenge gives engineers and engineering students the opportunity to do this and win up to $2 million. The race will be held at a yet-to-be-disclosed urban location in the Western United States, where a driverless vehicle must travel 60 miles.

Stanford University won the 2005 DARPA Grand Challenge, a 132-mile desert route, with a vehicle called Stanley. David Stavens, a Ph.D. candidate at Stanford and one of the co-designers/co-creators of Stanley is involved with Junior, a Stanford vehicle being designed for the 2007 race. “In terms of sensors, the biggest change between Stanley and Junior is that Stanley only needed to see stationary obstacles in front of him,” says Stavens. “Junior needs to see moving obstacle all around him.”

The primary sensor in Junior is Velodyne’s HD Lidar. The high definition (HD) sensor provides 3D information about the surrounding environment. With its 64 lasers spinning at about 15 to 16 rev/sec, the unit generates 2,621,440 points/sec to cover about a 50m range. Since the sensor rotates much faster than anything in the environment, it provides a sense of three dimensions. “Sixteen cycles per second is more than fast enough for any type of ground vehicle or pedestrian or bicycle tracking,” says Stavens. To detect objects beyond the range of the Velodyne HD Lidar, an Ibeo ALASCA XT Lidar provides measurements to distances over 200m. The unit has four echoes per plane and operates in four planes producing 16 echoes per measurement.

A Point Grey Ladybug2 provides the vision input. The unit uses six Sony 1/3-inch progressive scan CCD cameras with a resolution of 1024 × 768 and a frame rate of 30 frames/sec. Five cameras are positioned in a horizontal ring and one points straight up. The head unit uses a proprietary 1.2 Gbps optical link to the compressor unit that provides the ability to stream images at up to 30 frames/sec.

Stavens considers the Applanix pulse LV 420 system a key part of the sensing technology since it determines the vehicle’s location. The unit combines two dual-frequency GPS receivers, a high-performance inertial measurement unit (IMU), wheel odometery and OmniSTAR’s satellite-based differential correction service. Fusing all the inputs together in realtime provides an extremely accurate estimate of the vehicle’s location. “That turns out to be essential because when you are doing the sensor fusion of all these different sensors, one of the things that is really important is knowing precisely where the vehicle is when these measurements are being taken,” says Stavens.

The sensors, particularly the Ladybug2 and the Velodyne HD Lidar, produce a phenomenal amount of data. To communicate the data, the Veledyne, Ibeo and Applanix sensors use Ethernet. The Point Grey Ladybug2 uses FireWire 800. The vehicle’s computers process the instruments’ data as frequently as 200 times per second.

Since the sensors all exist, Stavens speculates several teams in the Urban Challenge will have a similar sensor suite, some type of laser combined with some type of camera. “So it really comes down to the software,” he says. “We think of this as a software competition — who can write the best artificial intelligence software.”

CMOS or CCD for Machine Vision?

CCD imagers were the first products in machine vision and have led the industry for many years. However, CMOS imagers are catching up quickly and are being implemented in many more applications than in previous years. When selecting an imager, a number of issues should be considered, relating both to the different characteristics of CCD/CMOS devices and the requirements of the application.

The technology gap between CCD and CMOS is getting narrower every month and the table below gives a comparison of characteristics of both technologies today.

CCD/CMOS CHARACTERISTICS COMPARISONS SPEED

CMOS has a speed advantage as onboard circuitry allows for low propagation delays and the conversion to digital closer to the pixels. CCD's can achieve high speeds, but at significant cost.

PROGRAMMABLE WINDOWING

CMOS has the ability of dynamically changing X,Y window locations, sizes and frame rates. Some CCD's now allow for several fixed windows that are not programmable.

NON UNIFORMITY

CCD's win this category as CMOS onboard amplifiers improve sensitivity but increase non uniformity, requiring additional software and hardware to reduce non uniformity.

RESPONSE

CMOS imagers have much higher signals in response to the same light levels due to amplifiers being placed at every pixel. This function is expensive and difficult to implement on CCD's.

GLOBAL SHUTTERS

Shuttering is superior in CCD's while maintaining large pixel size. CMOS gives up the larger pixel size for the shutter circuitry. Both families have versions of imagers that improve sensitivity but eliminate the global shutter and generally require the use of a mechanical shutter, which is not practical in most machine vision applications.

SIGNAL TO NOISE

The dynamic range of CCD's is much better due to lower noise. This is a key factor for the use of CCD's, but it should be noted that CMOS is advancing in this area with logarithmic response curves.

BLOOMING

Blooming is an inherent overexposure problem in CCD's that does not exist in CMOS. CCD's generally build in some type of anti-blooming circuitry to reduce the problem. CMOS also allows large dynamic logarithmic response to deal with high-intensity light applications.

INTERFACING

CMOS is a clear winner here with onboard circuitry including A/D and single supply. CCD's generally require multiple bias voltages, clock signals and external A/Ds, making interfacing bulky and expensive.

POWER CONSUMPTION

CCD's consume several times more power then CMOS.

COSTS

CCD technology is a custom process and therefore more expensive than CMOS, which is a standard process used to make most computer chips today.

COMPARISON BY APPLICATION TYPES

As can be seen by the comparison above, CMOS is rapidly catching up to CCD in many areas. However, high quality, lowlight images still give CCD's an advantage, but at higher costs.

We need to segment applications into a few categories in order to be able to decide how CCD and CMOS fit each of these machine vision applications.

STATIONARY OBJECT INSPECTION

These are applications where the object does not move and allows long exposure times or the ambient light is filtered out completely and a high- intensity strobe light source is used to stop or expose the object being inspected. Generally, imagers with global shutters are not required in these applications. Typical applications may be medical applications, automotive body manufacturing lines, license plate reading, some bar/matrix code applications, etc.

CCD — Depending on resolution and sensitivity requirements, the use of consumer type imagers including the large formats that require mechanical shutters, dark conditions or narrow bandwidth filters with strobed light sources. It should be noted that consumer imagers are mainly color and CCD's get very expensive in higher resolution monochrome.

CMOS — Rolling shutter consumer imagers can also be used as above with mechanical or strobed light sources. Again, most consumer imagers are color and hi-resolution monochrome are expensive.

Conclusion — Either imager can work in these applications with CMOS having a lower total cost.

LOW SPEED OBJECT INSPECTION

Typical low-speed 30-60fps applications are label inspection, bottling lines, slower 3D triangulation, bar code/matrix code, etc. Even though the frame rate is low, the shutter time of 1ms is likely needed to do the inspection. A global shutter is generally a requirement here along with a trigger signal to take the image.

CCD — 60fps requires the use of only low-resolution CCD color/monochrome imagers because CCD's generally require the full field of view be captured, limiting the frame rate for high resolution CCD imagers. A trigger signal is needed and multiple objects in FOV requires software extraction of the object of interest.

CMOS — Any resolution CMOS imager that has a global shutter and windowing can be used. The use of a trigger and windowing will allow a single image of the object of interest to be captured, potentially reducing image processing time and increasing frame rate. Free-running applications with no trigger can also be implemented by using the windowed high frame rate modes of CMOS imagers.

Conclusions — CCD has led this application area for many years, but the flexibility of CMOS is challenging now.

HIGH SPEED — 2D SURFACE INSPECTION APPLICATIONS

This category covers color and monochrome surface applications which generally involve one or more synchronized cameras and light sources inspecting various characteristics of a high-speed moving surface. Applications include webs (paper, steel, plastics, glass), roads, wood products, print, etc. These surfaces can be moving at speeds approaching 50m per second and require surface resolutions less then 1 mm. These speeds need a global shutter or exposure times approaching 20 µsec which necessitates intense light sources. Three types of imagers are used in these applications — linear CCD, area CCD and area CMOS. Each has it advantages and disadvantages.

Linear CCD — This is by far the most used imager in this application. Most engineers like to use one expensive large imager to cover the whole FOV to reduce the need to stitch multiple images in software. Generally, this involves mounting the camera with expensive optics far above the surface and lighting the surface with a very intense 100 percent duty cycle light source. Since the imager only sees a narrow row of pixels, most of the light hitting the surface is wasted energy. The large optics required generally need significant distortion correction due to the large FOV. High clock rates and multiple tap imagers are required to access the pixels in many of the high-speed applications.

Area CCD — These imagers can be used in multiple synchronized cameras with stitching of images resulting in much more efficient use of the light with inexpensive optics and short standoff distances. One major advantage to this technique is the use of a low-duty cycle light source as low as 0.2 percent which allows the use of over-driven pulse LED sources mounted at short standoffs. The challenge is manufacturing a large light source to light the full FOV of a CCD because of limited windowing ability. Bayer conversion for color can make the software more complex for stitching, etc. The advantage of low-duty cycle LED light sources now available from UV to IR enables the ability to do multi-spectral imaging in a single surface inspection camera by using different time windows.

Area CMOS — Same characteristics as area CCD with the added benefit that a programmable window enables a smaller low-duty cycle LED light source for a small FOV using a high frame rate window. In addition, CMOS imagers are available at much higher pixel clock speeds equivalent to linear line rates as high as 100K/sec.

Conclusion — There is no question the area imagers offer a clear advantage but require more complicated software and synchronization. The CMOS area imager with programmable windows is the simplest and provides highest speed implementation.

HIGH SPEED — 3D SURFACE INSPECTION APPLICATIONS

This category covers the use of triangulation and involves one or more synchronized monochrome imagers and laser light sources inspecting 3D characteristics of a high-speed, moving surface. Applications include glass, roads, wood products, tire, metal, rubber and plastic extrusions, etc. These 3D measurements are sometimes combined with 2D above and have similar speeds approaching 50m per second. These applications require cameras with effective frame rates approaching 50,000 fps for some applications.

CCD— Currently, most of these applications are not feasible with CCD's. Some of the smaller CCD's are able to read a small fixed window at a few thousand FPS, but clock speeds are limited.

CMOS — The best technology for these applications due to the high clock rate and dynamically programmable windowing ability of CMOS. Very high frame rates can be achieved with standard CMOS imagers with windows that move from frame to frame creating a high-speed moving FOV. Custom imagers have also been produced with multiple taps and onboard 3D processing logic that can achieve these high frame rates.

Conclusion: CMOS is the only technology here.

SUMMARY

In those machine vision applications requiring very high resolution, low light and low noise, use CCD's. Otherwise, a CMOS imager has the flexibility to solve most applications at lower total costs including the highest speed solutions.