calibration Module¶

Demos¶

• Basic auto-centering and calibration (notebook)

This is the module for calibration functions and data

skxray.calibration.estimate_d_blind(name, wavelength, bin_centers, ring_average, window_size, max_peak_count, thresh)¶

Estimate the sample-detector distance

Given a radially integrated calibration image return an estimate for the sample-detector distance. This function does not require a rough estimate of what d should be.

For the peaks found the detector-sample distance is estimated via .. math

D = \frac{r}{\tan 2\theta}

where \(r\) is the distance in mm from the calibrated center to the ring on the detector and \(D\) is the distance from the sample to the detector.

Parameters:

name : str The name of the calibration standard. Used to look up the expected peak location For valid options, see the name attribute on this function wavelength : float The wavelength of scattered x-ray in nm bin_centers : array The distance from the calibrated center to the center of the ring’s annulus in mm ring_average : array The average intensity in the given ring of a azimuthally integrated powder pattern. In counts [arb] window_size : int The number of elements on either side of a local maximum to use for locating and refining peaks. Candidates are identified as a relative maximum in a window sized (2*window_size + 1) and the same window is used for fitting the peaks to refine the location. max_peak_count : int Use at most this many peaks thresh : float Fraction of maximum peak height

Returns:

dist_sample : float The detector-sample distance in mm. This is the mean of the estimate from all of the peaks used. std_dist_sample : float The standard deviation of d computed from the peaks used.

skxray.calibration.refine_center(image, calibrated_center, pixel_size, phi_steps, max_peaks, thresh, window_size, nx=None, min_x=None, max_x=None)¶

Refines the location of the center of the beam.

This relies on being able to see the whole powder pattern.

Parameters:

image : ndarray The image calibrated_center : tuple (row, column) the estimated center pixel_size : tuple (pixel_height, pixel_width) phi_steps : int How many regions to split the ring into, should be >10 max_peaks : int Number of rings to look it thresh : float Fraction of maximum peak height window_size : int, optional The window size to use (in bins) to use when refining peaks nx : int, optional Number of bins to use for radial binning min_x : float, optional The minimum radius to use for radial binning max_x : float, optional The maximum radius to use for radial binning

Returns:

calibrated_center : tuple The refined calibrated center.