Prodction Diagram

Design Considerations

X-ray inspection is commonly used for security screening of baggage, such as checked and carry-on luggage at airports. The items to be inspected are subjected to x-ray radiation and the unabsorbed radiation passing through the items is collected on photo-detector (typically photodiode) arrays. These detectors output very low-level currents which require special signal conditioning and high resolution data converters are needed to achieve the required resolution to image the scanned items properly. Sometimes this signal conditioning is contained within a single-chip data acquisition solution such as the case where the current-to-voltage (I-to-V) conversion is included with the precision analog-to-digital converter (ADC). Other times discrete very low-current/noise front-end amplifiers measure and amplify the outputs from the photo-detector array and then drive stand-alone voltage-input ADCs.

The core system includes:

• DSP Processors
  • DSP processors can be used for image reconstruction needed to produce images of the scanned items from the signals received by the photo-detector arrays.
• Amplifiers
  • Very low-current and noise amplifiers are required to amplify the low-to-medium frequency signals from the photo-detector array for the ADC. These are usually the limiting component for the wide dynamic range needed. Due to varying signal magnitude, most often a low noise transimpedance amplifier (TIA) is needed.
• Converters
  • ADCs, normally delta-sigma types with integrated I-to-V conversion, can be used to convert the low-level current to digital information to be processed by the computing element.
  • Voltage input ADCs, typically are used when a separate front-end amplifier provides the I-to-V conversion.
  • DACs are most often used to create bias for the array.
• Power Management
  • Controls the system power, used by the acquisition system.
• Temperature Sensors
• There are normally many channels in a system causing the ambient temperature in the system to rise requiring fan-control cooling.