APPLICATIONS OF TECHNOLOGY:

	THE BERKELY LAB ALGORITHM CORRECTS NONLINEAR EFFECTS IN PHOTOGRAPHS
	The series of images above demonstrates the correction capabilities of the Berkeley Lab algorithm. Photo A is an original image which was saturated to obtain images B and C. The Berkeley Lab technique was applied to B and C to calibrate the detector. The calibration was then applied to B to obtain image D.

• Automatically correcting detector errors for
  • analog to digital converters (ADCs)
  • high and low-end CCDs
  • electron spectrometers and
    microscopes
  • x-ray imaging devices
• Extending the range of detectors

ADVANTAGES:

• Quantitatively characterizes the non-linear response of the detector and corrects the
  measured signals
• Eliminates the time and effort devoted to calibration and correcting drift
• Enables image correction when the object is uncharacterized

ABSTRACT:

Stefano Marchesini, Norman Mannella, and Charles Fadley of Berkeley Lab have developed an algorithm that quantitatively characterizes and corrects detector nonlinearity effects over the full dynamic range of the detection system. The algorithm is designed to replace standard calibration methods and enhance images and spectra obtained with any detector, including CCDs, electron microscopes and spectrometers, analogue to digital converters, and x-ray imagers.

Current methods employed to correct nonlinear effects require a complex, time consuming, and therefore costly procedure in which a known source, image, or spectra is used to calibrate the detector. Using the Berkeley Lab method to correct nonlinearities, an uncharacterized object can be imaged with two or more known exposure times and the algorithm calculates and corrects the overexposure.

Another disadvantage of traditional calibration methods is that once the device is calibrated, it starts to drift from the calibration standard. Since the Berkeley Lab solution to nonlinearities is an algorithm applied to each image set, the drifting is corrected anew for each final image.

The Berkeley Lab invention determines detector response from a least-squares analysis of the data acquired at different exposure times or incident fluxes. The technique can extend the calibration curve beyond the standard method of using a calibrated source.

STATUS:

• Patent Pending. Available for licensing or collaborative research

FOR MORE INFORMATION:

N. Mannella, S. Marchesini, A.W. Kay, A. Nambu, T. Gresch, S.-H. Yang, B.S. Mun, J.M. Bussat, A. Rosenhahn and C.S. Fadley, “Correction of Non-linearity Effects in Detectors for Electron Spectroscopy,” Journal of Electron Spectroscopy and Related Phenomena 2004, 141, 45-59.

SEE THESE OTHER BERKELEY LAB TECHNOLOGIES IN THIS FIELD:

• Transmission Electron Microscope Phase-contrast Enhancement, IB-2036
• High Efficiency Micro-Scale Light-Concentrating Arrays for Digital Imaging, IB-2279
• High Quantum Efficiency Charge-Coupled Device, IB-1204a
• High Voltage Compatible, Fully Depleted CCD, IB-2028