Developments in personal computer hardware and Windows-based software are moving the technology for laser-beam profiling into a realm of relatively high user-friendliness and low cost that might be compared to the status of the voltmeter in electronics, according to Gary Forrest, president of SensorPhysics (Oldsmar, FL). Not everyone in the beam-profiler business agrees with that comparison, but Forrest has carved out an aggressively price-competitive niche by designing his software for use with low-cost Video for Windows-based frame grabbers and PC card interfaces.
Last spring SensorPhysics began offering its source code for free over the Internet, which led to a doubling of sales volume for the $1000 software, frame grabber, and cable package. "Twice as many people buy it now," said Forrest. "And as many people buy it as take it for free." Even though the SensorPhysics website describes how the Video-for-Windows strategy is implemented and provides vendor information for compatible frame-grabber cards along with the source code, the number of users who have chosen to pay $1000 to SensorPhysics for a turnkey system is the same as those who have chosen to simply take the software and purchase a compatible frame grabber separately for about $100.
"People recognize this is a tool they need, and at $1000 it's not that expensive a tool anymore," Forrest said. "It's becoming more like a voltmeter in the electrical world." The $1000 SensorPhysics system provides 8 bits of resolution for 320 by 240 pixels at a 30-Hz live-mode refresh rate (see figure).
Filling the niche
Predictably perhaps, the aggressively priced beam-profiler niche has already attracted competitors. About six months ago, Ophir (Danvers, MA) introduced two versions (one ultraviolet and one visible) of a beam-profiler based on a PC connection to a low-cost frame grabber that operates from 200 to 1100 nm, and it is planning to introduce a third system to go up to 1.8 µm later this year.
"We've taken this particular step in several cases," said Dick Reiley, sales director. "Not just in beam profilers, but we're also doing it in a spectrometer, and we have other equipment coming out that will operate off of a parallel port or off of a PCI-card type of device." Taking advantage of the ubiquitous and relative low cost of Windows-based PCs in research and engineering environments allows the vendor to focus on the detector rather than the instrumentation and frees the customer from purchasing dedicated equipment that might not be necessary, Reiley said. The Ophir software is not yet available for free download, but Reiley says it will be when the final version is ready.
The 8-bit, 460 x 640-pixel Ophir system, which includes the detector, operates at a 30-Hz frame rate and can go up to 10 kHz on pulsed lasers. "When we developed our specification, we chose to have a $3100 finished product that included hardware and software," he said. "I'm sure that there are faster and more complex ones out there, but all of the ones that we have sold to date seemed to be fast enough with a very high level of accuracy."
The "Mercedes-Benz" of voltmeters
Carlos Roundy, president of Spiricon (Logan, UT) uses transportation rather than electrical metaphors to describe beam-profiler performance. Across the range of possible vehicles, he describes the Spiricon measurement systems (1024 x 1024 pixels at 15 to 20 Hz depending on the camera; 8-, 10-, and 12-bit frame grabbers; and an ability to display real-time camera frame rates at 30 to 60 Hz) as the "Mercedes Benz."
"The reason we haven't gone to a PC card is that they're too slow and can't handle the data," Roundy said. "They can't handle enough bits. We're moving in the direction of a new infrared camera that we're coming out with. It's going to have a FireWire output, so we will go directly into the computer with no frame grabber at all."
Spiricon does not make its software freely available because of its complexity. "We would have to have five people on the phone continuously solving people's problems if they got into our code and started making changes," Roundy said. The Spiricon software also includes patented algorithms to boost the accuracy of beam-width calculations. "There is a need for the low-cost frame-grabber type of system in the market for people who don't need the accuracy, precision and capability that we've got," Roundy said. But Spiricon uses only industrial grade cameras in the $1000 range.
A Spiricon system might include a $1000 camera and a $1000 computer, Roundy said. Then the frame grabber and software range from an 8-bit at $3500 to a 12-bit at $4500.
Assessing the complications
Derrick Peterman, a sales engineer at Photon Inc. (San Jose, CA), and Roger Rypma, marketing manager in the Coherent Instruments Division (Auburn, CA), characterized the voltmeter comparison as an oversimplification. Peterman said the comparison would only be valid for simpler systems. "Beam profiling is fairly straightforward in measuring something like a 1-mW HeNe," he said. "But when you start getting to a high-energy pulsed beam or if you want to measure features in your beam that are less than 5 µm wide, it then requires more sophisticated analysis or a more sophisticated optical setup."
Wavelength is another factor he said. In the visible wavelengths, consumer demand for digital cameras and camcorders has already spawned a strong detector technology and supply. Infrared sensors have not yet been developed to that degree, however, even though current optical telecom demand is likely to eventually improve near-infrared technology. Photon produces three main families of beam profilers: beam scanners, goniometric radiometers, and fiberoptic analyzers, which all rely on the more expensive frame grabbers, Peterman said. Their low-end systems ($4000 to $5000) have half-inch sensors, matrix sizes of 768 x 494, 30-Hz refresh rates and 8-bit resolution.
Rypma said the personal computer is not the biggest trend in evolving beam profiler technology and products. "Of course PC capabilities are important because of the development of the PC industry," he said. "But the major focus is the transition to digital cameras. The fundamental reason driving that has nothing to do with the computer. It has to do with getting more dynamic range out of the sensor to make more accurate measurements."
Coherent's main beam-profiling system, which sells for just under $5000 (camera, software, and interface for cabling), has replaced the frame grabber with a 10-bit digital camera going into a 764 x 494 chip. One current limitation on the digital chips is smaller arrays, Rypma said. So the digital system, with quarter-inch and half-inch arrays, is not yet available at two-thirds of an inch. So the company offers an analog system with a frame grabber and a two-thirds inch format, while the larger digital format is under development for applications where beam size, shape, or wavelength needs that cannot be handled by the digital system.
Despite the advances in both computers and digital imaging, Rypma emphasized that beam profiling will never become "idiot proof." The reason for that is the continued need to match equipment configuration to a proposed application. "You still have to do your homework," he said. "It's like using a 'voltmeter.' You need to zero it out first."