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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"
#include "diffraction.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)
/* Radius of X-ray beam */
#define BEAM_RADIUS (3.0e-6)
/* 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] = (uint16_t)tmp[x + width*y];
}
}
free(tmp);
free(hdr);
return data;
}
void record_image(struct image *image)
{
int x, y;
double fluence;
double ph_per_e;
double sa_per_pixel;
double area;
const int do_bloom = 1;
/* How many photons are scattered per electron? */
area = M_PI*pow(BEAM_RADIUS, 2.0);
fluence = PULSE_ENERGY_DENSITY / image->xray_energy;
ph_per_e = fluence * pow(THOMSON_LENGTH, 2.0);
printf("Fluence = %5e photons / m^2, %5e photons total\n",
fluence, fluence*area);
/* Solid angle subtended by a single pixel at the centre of the CCD */
sa_per_pixel = pow(1.0/(image->resolution * image->camera_len), 2.0);
printf("Solid angle of one pixel (at centre of CCD) = %e sr\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, intensity, sa, water;
double complex val;
val = image->sfacs[x + image->width*y];
intensity = pow(cabs(val), 2.0);
/* Add intensity contribution from water */
water = water_intensity(image->qvecs[x + image->width*y],
image->xray_energy,
BEAM_RADIUS, 1.5e-6);
//printf("%e, %e, ", intensity, water);
intensity += water;
/* 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;
//printf("%e counts\n", counts);
counts += poisson_noise(counts);
image->hdr[x + image->width*y] = counts;
}
progress_bar(x, image->width-1, "Adding water and noise");
}
if ( do_bloom ) {
image->data = bloom(image->hdr, image->width, image->height);
} else {
image->data = malloc(image->width * image->height
* sizeof(uint16_t));
for ( x=0; x<image->width; x++ ) {
for ( y=0; y<image->height; y++ ) {
double val;
val = image->hdr[x + image->width*y];
if ( val > SATURATION ) val = SATURATION;
image->data[x + image->width*y] = (uint16_t)val;
}
}
}
}
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