def _onSpotImage(self, df, data):
"""
Receives the Spot image data
"""
if self.bgsub:
data = Subtract(data, self.bg_image)
self._spot_images.append(data)
self._ccd_done.set()
logging.debug("Got Spot image!")
def _onCCDImage(self, df, data):
"""
Receives the CCD data
"""
try:
if data.metadata[model.MD_ACQ_DATE] < self._min_acq_time:
logging.debug("Received a CCD image too early")
return
except KeyError:
pass
if self.bgsub:
self._optical_image = Subtract(data, self.bg_image)
else:
self._optical_image = data
self._ccd_done.set()
logging.debug("Got CCD image!")
def SubstractBackground(ccd, det_dataflow=None):
"""
Performs optical acquisition with background substraction. Particularly
used in order to eliminate the source background in Delphi.
ccd (model.DigitalCamera)
det_dataflow (model.DataFlow): dataflow of se- or bs- detector
enabled (boolean): if True, apply background substraction
returns (model.DataArray):
Image with substracted background
"""
if det_dataflow is not None:
bg_image = ccd.data.get(asap=False)
det_dataflow.subscribe(_discard_data)
image = ccd.data.get(asap=False)
ret_data = Subtract(image, bg_image)
det_dataflow.unsubscribe(_discard_data)
return ret_data
else:
image = ccd.data.get(asap=False)
return image
def AcquireNoBackground(ccd, dfbkg=None):
"""
Performs optical acquisition with background subtraction if possible.
Particularly used in order to eliminate the e-beam source background in the
Delphi.
ccd (model.DigitalCamera): detector from which to acquire an image
dfbkg (model.DataFlow or None): dataflow of se- or bs- detector to
start/stop the source. If None, a standard acquisition is performed (without
background subtraction)
returns (model.DataArray):
Image (with subtracted background if requested)
"""
if dfbkg is not None:
bg_image = ccd.data.get(asap=False)
dfbkg.subscribe(_discard_data)
image = ccd.data.get(asap=False)
dfbkg.unsubscribe(_discard_data)
ret_data = Subtract(image, bg_image)
return ret_data
else:
image = ccd.data.get(asap=False)
return image
def FindEbeamCenter(ccd, detector, escan):
"""
Locate the center of the SEM image by setting the SEM to spot mode and
measuring the position of the spot on the CCD. It is mostly targeted at
doing it fast. In particular it doesn’t do any focusing or multiple
iterations with feedback loop.
ccd (model.DigitalCamera): The ccd
detector (model.Detector): The se-detector
escan (model.Emitter): The e-beam scanner
return (tuple of 2 floats): x, y position of the spot relative to the
center of the CCD.
raise:
LookupError: if the spot cannot be found
"""
logging.debug("Starting ebeam spot detection...")
# save the hw settings
prev_exp = ccd.exposureTime.value
prev_bin = ccd.binning.value
prev_res = ccd.resolution.value
try:
# set the CCD to maximum resolution
ccd.binning.value = (1, 1)
ccd.resolution.value = ccd.resolution.range[1]
# set ebeam to spot mode
# resolution -> translation: order matters
escan.resolution.value = (1, 1)
# put a not too short dwell time to avoid acquisition to keep repeating,
# and not too long to avoid using too much memory for acquiring one point.
escan.dwellTime.value = escan.dwellTime.range[1] # s
# Subscribe to actually set the spot mode
detector.data.subscribe(discard_data)
exp = 0.1 # start value
prev_img = None
while exp < 2: # above 2 s it means something went wrong
ccd.exposureTime.value = exp
img = ccd.data.get(asap=False)
if prev_img is not None:
img += prev_img # accumulate, to increase the signal
try:
coord = FindSpot(img, sensitivity_limit=10)
except LookupError:
# spot was not found, subtract background and try again
logging.debug("Subtracting background image")
detector.data.unsubscribe(discard_data)
bg_image = ccd.data.get(asap=False)
detector.data.subscribe(discard_data)
img = Subtract(img, bg_image)
try:
coord = FindSpot(img, sensitivity_limit=10)
except LookupError:
# try again with longer exposure time
prev_img = img
exp *= 2
continue
# found a spot! => convert position to meters from center
return _ConvertCoordinates(coord, img)
finally:
detector.data.unsubscribe(discard_data)
ccd.exposureTime.value = prev_exp
ccd.binning.value = prev_bin
ccd.resolution.value = prev_res
raise LookupError("Failed to locate spot after exposure time %g s" % exp)