Honour voltage from MRC header if present

git-svn-id: svn://cook.msm.cam.ac.uk:745/diff-tomo/dtr@11 bf6ca9ba-c028-0410-8290-897cf20841d1

3 files changed, 19 insertions, 1 deletions

diff --git a/src/mrc.c b/src/mrc.c
index 26b43cb..a01809c 100644
--- a/src/mrc.c
+++ b/src/mrc.c
@@ -21,6 +21,7 @@
 #include "imagedisplay.h"
 #include "itrans.h"
 #include "reflections.h"
+#include "utils.h"
 
 int mrc_read(ControlContext *ctx) {
 
@@ -111,7 +112,11 @@ int mrc_read(ControlContext *ctx) {
 		
 		printf("Image #%3i: tilt=%f omega=%f L=%f\t", i, ext[i].a_tilt, ext[i].tilt_axis, ext[i].magnification);
 		ctx->camera_length = ext[i].magnification;
-		ctx->lambda = 2.51e-12;	/* 200kV. Fudged until Max puts the HT voltage in the MRC headers */
+		if ( ext[i].voltage == 0 ) {
+			ctx->lambda = lambda(200000);
+		} else {
+			ctx->lambda = lambda(1000*ext[i].voltage);
+		}
 		ctx->omega = ext[i].tilt_axis;
 		ctx->pixel_size = ext[i].pixel_size;
 		
diff --git a/src/utils.c b/src/utils.c
index ce7c7f3..4055676 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -42,3 +42,15 @@ double angle_between(double x1, double y1, double z1, double x2, double y2, doub
 	return ((acos((x1*x2 + y1*y2 + z1*z2) / (mod1*mod2)))/M_PI) * 180;
 
 }
+
+/* Wavelength of an electron (in m) given accelerating potential (in V) */
+double lambda(double V) {
+
+	double m = 9.110E-31;
+	double h = 6.625E-34;
+	double e = 1.60E-19;
+	double c = 2.998E8;
+	
+	return h / sqrt(2*m*e*V*(1+(e*V / 2*m*c*c)));
+
+}
diff --git a/src/utils.h b/src/utils.h
index 10ef3eb..b4a0dca 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -20,5 +20,6 @@ extern unsigned int smallest(signed int a, signed int b);
 extern double distance(double x1, double y1, double x2, double y2);
 extern double modulus(double x, double y, double z);
 extern double angle_between(double x1, double y1, double z1, double x2, double y2, double z2);
+extern double lambda(double voltage);
 
 #endif	/* UTILS_H */