Among those companies opting for the multiple CCD configuration are Swissray International Inc. (New York), which uses four CCD cameras, and Wuestec Medical Inc. (Mobile, Ala.), which uses two CCD cameras in its current system. Yet, at press time, Wuestec said it is in the process of finalizing a single-CCD system due for release in April.
Cost of CCD Digital X-Ray
The advantages and disadvantages to the different configurations vary depending on the source, but there are definitely some effects.
According to Steve McArthur, CEO of SpectraSource Instruments (Westlake Village, Calif.), a CCD camera maker, the number of CCDs used will vary depending on the marketing objectives of the company and the type of product it's looking to market.
"One company may want to target the high end and get the highest resolution possible," says McArthur, adding that those companies would be more likely to use multiple CCDs. "Another company may want to make low-cost systems and deal with performance compromises to keep the cost down."
Cost is an issue that can't be ignored in any review of DR technologies. Logic would follow that a multiple CCD configuration would mean a higher list price due to the technology involved, but not always.
Ueli Laupper, CEO of Swissray America Inc. (New York), agrees with that assessment, but offers a justification of the increase in system cost. He feels that using multiple CCDs allows the customer to use the system for a variety of applications and, in doing so, reduces the cost of purchasing additional systems for those applications.
"Obviously, if you use more CCDs, you increase the cost," says Laupper. "But if you have a single CCD, you cannot provide a multi-functional direct digital radiography unit because you cannot provide enough spatial resolution for general radiography."
Imaging Dynamics is a newcomer to the CCD market and looks to maximize the single-CCD's ability to reduce costs. Company officials say its Xplorer 1000 is listing for $90,000, yet produces comparable images to $400,000 systems.
"While we may have had to build a much fancier lens to bring the whole image into our one CCD, the fact of the matter is we've only got one CCD," explains Robin Winsor, CTO at Imaging Dynamics. "So we can build it more cheaply and our raw material costs are less. And you can see that by the relative selling prices of our units."
CCD Sensors and Image Capture: How It Works
Below is a step-by-step explanation of the CCD sensor and its role in the digital image capture process.
1. Mechanical shutter opens, exposing the
CCD sensor to light.
2. Light is converted to charge in the CCD.
3. The shutter closes, blocking the light.
4. The charge is transferred to the CCD
output and converted to a signal.
5. The signal is digitized, and the digital
data is captured in memory.
6. The captured image is processed and
displayed on the camera LCD or computer.
CCD imaging is performed in a three-step process:
1. Exposure, which converts light into an
electronic charge at discrete sites called
pixels.
2. Charge transfer, which moves the packets
of charge within the silicon substrate.
3. Charge-to-voltage conversion and output
amplification.
