Changeset 17994 for trunk/psModules/src/detrend/pmShutterCorrection.h
- Timestamp:
- Jun 8, 2008, 2:39:37 PM (18 years ago)
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- 1 edited
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trunk/psModules/src/detrend/pmShutterCorrection.h (modified) (5 diffs)
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trunk/psModules/src/detrend/pmShutterCorrection.h
r17228 r17994 5 5 * @author Paul Price, IfA 6 6 * 7 * @version $Revision: 1.1 5$ $Name: not supported by cvs2svn $8 * @date $Date: 2008-0 3-29 03:10:17 $7 * @version $Revision: 1.16 $ $Name: not supported by cvs2svn $ 8 * @date $Date: 2008-06-09 00:39:37 $ 9 9 * Copyright 2006 Institute for Astronomy, University of Hawaii 10 10 */ … … 16 16 /// @{ 17 17 18 /* A mechanical shutter may not yield uniform exposure times as a function of 19 * position on the detector. The typical error consists of a constant 20 * exposure-time offset relative to the requested value, ie exposure time is 21 * T_o + dT(x,y). The exposure error, dT, may be measured with the following 22 * scheme. Obtain a set of exposures with different exposures times taken of 23 * the same flat-field source; the source must be spatially stable between the 24 * exposures, but need not have a stable amplitude. For an illuminating flux 25 * of intensity F(x,y) = F_o f(x,y), the signal recorded by any pixel in the 26 * detector is given by: S(t,x,y) = F_o(t) f(x,y) (T_o + dT(x,y)) where F_o is 27 * the F_o(t) is the (variable) overall intensity of the illuminating source 28 * and f(x,y) is the spatial illumination patter times the flat-field response. 29 * Choose a reference location in the image (eg, the detector center) and 30 * divide by the value of that region (ie, mean or median): 18 /* A mechanical shutter may not yield uniform exposure times as a function of position on the 19 * detector. The typical error consists of a constant exposure-time offset relative to the 20 * requested value, ie exposure time is T_o + dT(x,y). The exposure error, dT, may be 21 * measured with the following scheme. Obtain a set of exposures with different exposures 22 * times taken of the same flat-field source; the source must be spatially stable between the 23 * exposures, but need not have a stable amplitude. For an illuminating flux of intensity 24 * F(x,y) = F_o f(x,y), the signal recorded by any pixel in the detector is given by: S(t,x,y) 25 * = F_o(t) f(x,y) (T_o + dT(x,y)) where F_o(t) is the (variable) overall intensity of the 26 * illuminating source and f(x,y) is the spatial illumination pattern times the flat-field 27 * response. Choose a reference location in the image (eg, the detector center) and divide by 28 * the value of that region (ie, mean or median): 31 29 * 32 30 * s(t,x,y) = S(t,x,y) / S(t,0,0) … … 34 32 * s(t,x,y) = f(x,y) (T_o + dT(x,y)) / f(0,0) (T_o + dT(0,0)) 35 33 * 36 * we can absorb the term f(0,0) into f(x,y) as we have no motivation for the 37 * scale of f(x,y). For any single pixel, over the set of exposures, we thus38 * need to solve for dT(x,y), dT(0,0), and f'(x,y) in the equation:39 * s(t,x,y) = f'(x,y) (T_o + dT(x,y)) / (T_o + dT(0,0))34 * we can absorb the term f(0,0) into f(x,y) as we have no motivation for the scale of f(x,y) 35 * -- a normalization for the flat-field is not specified here. For any single pixel, over 36 * the set of exposures, we thus need to solve for dT(x,y), dT(0,0), and f'(x,y) in the 37 * equation: s(t,x,y) = f'(x,y) (T_o + dT(x,y)) / (T_o + dT(0,0)) 40 38 * 41 39 * we avoid directly fitting these values as the process would be a non-linear … … 62 60 /// Shutter correction parameters, applicable for a single pixel 63 61 typedef struct { 64 double scale; ///< The normalisation for an exposure, A(k) 62 double scale; ///< The normalisation for an exposure, A(k) or f'(x,y) 65 63 double offset; ///< The time offset, dTk 66 64 double offref; ///< The reference time offset, dTo 67 65 int num; ///< Number of points used 68 66 float stdev; ///< Standard deviation 67 bool valid; // is the fitted shutter correction valid (produce a significant improvement?) 69 68 } pmShutterCorrection; 70 69 … … 173 172 /// Calculate the reference shutter time from the correction data 174 173 float pmShutterCorrectionReference( 175 constpmShutterCorrectionData *data ///< Correction data174 pmShutterCorrectionData *data ///< Correction data 176 175 ); 177 176
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