Product's abilities were misstated

April 1, 2001
I want to clarify a few points mentioned in your February article on Software and Computing ("Personal computer technology simplifies beam profiling," Laser Focus World, February 2001, p. 149).

I want to clarify a few points mentioned in your February article on Software and Computing ("Personal computer technology simplifies beam profiling," Laser Focus World, February 2001, p. 149). First, our capture resolution is 640 x 480 with a PCI frame grabber. The 320 x 240 value you quote is for our USB-based LaserTest and is limited by the USB hardware.

Also, it is generally assumed that inexpensive PC-based video cards are slow. In fact, most operate at 30 Hz video rates with no problem. The "slow" aspect is the ability of beam-profiling software to false color the images—something the LaserTest software does very efficiently. Yes, software does count.

Next, confusion still reigns with regard to the usefulness of more than 8 bits of data. For CCD-based beam profiles the noise is proportional to the square root of the signal. Since in beam profiling the signal is typically very close to saturation this is the major source of noise—one not improved by higher resolution systems. Using a faster shutter speed does achieve greater resolution, but by reducing noise—something that 8-bit systems benefit from as well.

Finally, there was the suggestion that there are wavelength limitations, especially at 1.5-µm telecom wavelengths. We have utilized infrared vidicon cameras from Hamamatsu for many years and the Sensors Unlimited InGaAs array cameras are routinely demonstrated with our software by that company, so wavelength really is not an issue when it comes to getting beam profile data quickly and easily.

Gary Forrest
SensorPhysics
105 Kelleys Trail
Oldsmar, FL 34677

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CorrectionIn the market review, "Review and forecast of the laser markets Part II: Diode lasers," published in the February issue of Laser Focus World, the market sales and unit totals by year in the sector snapshot boxes were incorrect. Correct numbers may be viewed in the article at www.laser-focus.com; go to "Archives" and select February 2001. We apologize for the inconvenience.

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