What was the period in japan's history in the late 19th century when imperial rule was restored known as?

The answer is Meiji period also known as Meiji Restoration.

This was a major event in Japanese history that restored the Imperial rule over all of Japan. It is named after the Emperor Meiji.

The Meiji period is usually defined between 1868 - 1912 which also saw nation-wide social and economic reforms.

The Meiji period was critical in bringing advanced learning and scientific knowledge to the Japanese society.