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/*
* detector.c
*
* Detector properties
*
* (c) 2007-2009 Thomas White <thomas.white@desy.de>
*
* pattern_sim - Simulate diffraction patterns from small crystals
*
*/
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include "image.h"
#include "utils.h"
/* Pulse energy density in J/m^2 */
#define PULSE_ENERGY_DENSITY (30.0e7)
/* Detector's quantum efficiency */
#define DQE (0.9)
/* Detector's saturation value */
#define SATURATION (60000)
/* Bleed excess intensity into neighbouring pixels */
static void bloom_values(double *tmp, int x, int y,
int width, int height, double val)
{
double overflow;
overflow = val - SATURATION;
/* Intensity which bleeds off the edge of the detector is lost */
if ( x > 0 ) {
tmp[x-1 + width*y] += overflow / 6.0;
if ( y > 0 ) {
tmp[x-1 + width*(y-1)] += overflow / 12.0;
}
if ( y < height-1 ) {
tmp[x-1 + width*(y+1)] += overflow / 12.0;
}
}
if ( x < width-1 ) {
tmp[x+1 + width*y] += overflow / 6.0;
if ( y > 0 ) {
tmp[x+1 + width*(y-1)] += overflow / 12.0;
}
if ( y < height-1 ) {
tmp[x+1 + width*(y+1)] += overflow / 12.0;
}
}
if ( y > 0 ) {
tmp[x + width*(y-1)] += overflow / 6.0;
}
if ( y < height-1 ) {
tmp[x + width*(y+1)] += overflow / 6.0;
}
}
static uint16_t *bloom(double *hdr_in, int width, int height)
{
int x, y;
uint16_t *data;
double *tmp;
double *hdr;
int did_something;
data = malloc(width * height * sizeof(uint16_t));
tmp = malloc(width * height * sizeof(double));
hdr = malloc(width * height * sizeof(double));
memcpy(hdr, hdr_in, width*height*sizeof(double));
/* Apply DQE (once only) */
for ( x=0; x<width; x++ ) {
for ( y=0; y<height; y++ ) {
hdr[x + width*y] *= DQE;
}
}
do {
memset(tmp, 0, width*height*sizeof(double));
did_something = 0;
for ( x=0; x<width; x++ ) {
for ( y=0; y<height; y++ ) {
double hdval;
hdval = hdr[x + width*y];
/* Pixel not saturated? */
if ( hdval <= SATURATION ) {
tmp[x + width*y] += hdval;
continue;
}
bloom_values(tmp, x, y, width, height, hdval);
tmp[x + width*y] += SATURATION;
did_something = 1;
}
}
/* Prepare new input if we're going round for another pass */
if ( did_something ) {
memcpy(hdr, tmp, width*height*sizeof(double));
}
} while ( did_something );
/* Turn into integer array of counts */
for ( x=0; x<width; x++ ) {
for ( y=0; y<height; y++ ) {
data[x + width*y] = tmp[x + width*y];
}
}
free(tmp);
free(hdr);
return data;
}
void record_image(struct image *image)
{
int x, y;
double ph_per_e;
double twotheta_max, np, sa_per_pixel;
/* How many photons are scattered per electron? */
ph_per_e = PULSE_ENERGY_DENSITY * pow(THOMSON_LENGTH, 2.0)
/ image->xray_energy;
printf("%e photons are scattered per electron\n", ph_per_e);
twotheta_max = image->twotheta[0];
np = sqrt(pow(image->x_centre, 2.0) + pow(image->y_centre, 2.0));
sa_per_pixel = pow(2.0 * twotheta_max / np, 2.0);
printf("sa per pixel=%e\n", sa_per_pixel);
image->hdr = malloc(image->width * image->height * sizeof(double));
for ( x=0; x<image->width; x++ ) {
for ( y=0; y<image->height; y++ ) {
double counts;
double intensity;
double sa;
double complex val;
val = image->sfacs[x + image->width*y];
intensity = val * conj(val);
/* What solid angle is subtended by this pixel? */
sa = sa_per_pixel * cos(image->twotheta[x + image->width*y]);
counts = intensity * ph_per_e * sa;
image->hdr[x + image->width*y] = counts;
}
}
image->data = bloom(image->hdr, image->width, image->height);
}
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