Depth Determination in X-ray Backscatter System Using Frequency Modulated X-Ray Beam

摘要

An X-ray backscatter imaging system uses frequency modulated X-rays to determine depth of features within a target. An X-ray source generates X-ray radiation modulated by a frequency-modulated bias current. The X-ray radiation impinges upon and is backscattered from multiple depths within the target. A scintillating material receives the backscattered X-rays and generates corresponding photons. A photodetector, having gain modulated by the frequency modulation signal from the local oscillator, receives the photons from the scintillating material and generates an analog output signal containing phase delay information indicative of the distance travelled by the X-rays backscattered from multiple depths within the target. The analog output signal is sampled by an analog-to-digital converter to create a digital output signal. A computer processor performs a discrete Fourier transform on the digital output signal to provide target depth information based on the phase delay information.

主权项

1. An X-ray backscatter imaging system comprising:
a modulation signal source for generating a frequency modulation signal; a magnetic field generator for generating a magnetic field; means for modulating the magnetic field with the frequency modulation signal to provide a frequency-modulated magnetic field; an X-ray radiation source disposed adjacent the magnetic field generator and generating X-ray radiation modulated by the frequency-modulated magnetic field, wherein the X-ray radiation impinges upon and penetrates a target, and is backscattered from multiple depths within the target; scintillating material for receiving X-ray radiation backscattered from the multiple depths within the target and for generating photons corresponding to the backscattered X-ray radiation; a bias signal source for generating a bias signal; means for modulating the bias signal with the frequency modulation signal to provide a frequency-modulated bias signal; photon detection means for receiving the photons generated by the scintillating material, receiving the frequency-modulated bias signal, and generating an analog output signal based thereon, wherein the analog output signal contains phase delay information indicative of distance travelled by the X-ray radiation backscattered from the multiple depths within the target; an analog-to-digital converter for sampling the analog output signal at a sampling frequency and converting the analog output signal to a digital output signal; and a computer processor for receiving the digital output signal and performing a discrete Fourier transform on the digital output signal to provide target feature depth information based on the phase delay information.