Non-intrusive measurement of the pitch of a blade

A blade pitch measuring device of an un-ducted fan of a turbomachine, the fan comprising:

• a. a hub,
• b. at least one platform rotatable with respect to the hub and
• c. at least one blade mounted on the platform,
• wherein:
• at least one first visual marker attached to the platform,
• at least one second visual marker attached to the hub, the first and the second visual marker forming a pattern which evolves depending on the pitch of the blade and
• at least one optical acquisition device, the optical acquisition device being configured to capture an image of the pattern so as to deduce the pitch of the blade from the image of the pattern,
• wherein the device also includes a processing module including a memory, a processor and a communication device, the communication device being configured to communicate the images captured by the optical acquisition device to the processor, the memory including instructions, the processor being configured to implement the instructions of the memory so as to detect the pattern in the image and to deduce the pitch of the blade from the pattern, and
• wherein the blade pitch measuring device further comprises:
• a motor configured to rotatable drive the hub, and
• a device for acquiring an angular position of the hub configured to deliver a signal depending on the angular position of the hub,
• the processor being configured to cause the triggering of the optical acquisition device depending on the signal.