diff --git a/doc/ptu_d46_calibration.md b/doc/ptu_d46_calibration.md
index 983489fa97dfe0695031529eb163f52577d3ed69..8fdc912a9991dca14ea8ee774f0f6e037c5eb5a3 100644
--- a/doc/ptu_d46_calibration.md
+++ b/doc/ptu_d46_calibration.md
@@ -8,7 +8,7 @@
 6. Screw the shaft's gripper.
 7. Close both servos.
 
-**Opened pan&tilt unit detail**
+**Open pan&tilt unit detail**
 
 <img src="doc/images/ptu_d46_pan_calibration.jpg" alt="ptu_d46_pan_calibration" height="300">
 <img src="doc/images/ptu_d46_tilt_calibration.jpg" alt="ptu_d46_tilt_calibration" height="300">
\ No newline at end of file