Update README.md

README.md

@@ -54,7 +54,7 @@ In the preference pane, software and hardware triggering can be selected. The ca
 With commercial projectors you can usually project 60 patterns per second at most (LC4500 allows for 120 8-bit patterns per second). Usually the camera requires a pause between two consecutive exposures, and you will need to waste one refresh period. With LC4500 we can project 60 grayscale patterns per second resulting in up to 20 point clouds per second.
 
 ### Calibration
-Calibration of your hardware setup determines the internal camera and projector parameters, and the relative position of the projector relative to the camera. The calibration procedure only is seen in the video above, and requires a flat board with a grey-white checkerboard printed onto it. Good calibration requires a large number of calibration positions covering all of the sensor field of view and with some foreshortening (angle of the calibration board relative to view-axis).
+Calibration of your hardware setup determines the internal camera and projector parameters, and the relative position of the projector relative to the camera. The calibration procedure only is seen in the video above, and requires a flat board with a grey-white checkerboard printed onto it. Good calibration requires a large number of calibration positions covering all of the sensor field of view and with some foreshortening (angle of the calibration board relative to view-axis). You can use e.g.  https://calib.io/pages/camera-calibration-pattern-generator to generate a PDF for the checkerboard.
 
 ### Codec
 SLStudio serves as a structured light platform. A number of encoding strategies has been implemented, and these differ greatly in the number of patterns, accuracy and robustness to e.g. shiny or semitransparent surfaces. For many applications, 2x3 phase shifting provides good results. It uses 6 patterns, so you will reach 10Hz point cloud update frequency with the appropriate hardware.