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authorWerner Almesberger <werner@almesberger.net>2015-03-13 05:01:41 (GMT)
committerWerner Almesberger <werner@almesberger.net>2015-03-13 05:04:14 (GMT)
commit48d536ba91ed291a59d47a54ff23fd3dd0c463d1 (patch)
treea1709687054b2b0a51eceab89ad7542016d82394
parent6832e6205799ebc682cb7ff6ead2078841367531 (diff)
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README: add scanning needle parameters and correction function
-rw-r--r--README29
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diff --git a/README b/README
index 5854803..12ce616 100644
--- a/README
+++ b/README
@@ -1,4 +1,5 @@
Workflow
+--------
3D scans:
@@ -20,3 +21,31 @@ Pictures:
- mv foo.jpg pics/large/
- ./smallpics
- git commit
+
+
+Correcting for the shape of the scanning needle
+-----------------------------------------------
+
+Needle shape:
+- tip diameter: 80 um
+- cone length: ~ 7 mm
+- cone diameter: 1 mm
+
+Correction for needle shape at an edge (vertical drop):
+
+z' = measured depth (larger values are deeper)
+z = real depth
+x = distance from edge
+r = cone diameter / 2
+d = cone diameter
+a = (d - tip diameter) / cone length / 2 = 0.066
+
+x < 0: z' = z
+x < 0 < r: z' = z + r - sqrt(r^2 - x^2)
+x > r: z' = z + r + (x - r) / a
+x > d / 2: not applicable
+
+In gnuplot syntax:
+
+a=.92/7/2
+plot x < 0 ? 0 : x < r ? r-sqrt(r*r-x*x) : r+(x-r)/a