SenseTime Group has raised $620 million at a valuation of more than $4.5 billion just months after scoring a similar amount from investors led by Alibaba and Singapore’s state investment firm.

Fidelity International and Silver Lake Partners were among the investors in the latest financing, bringing the total amount raised by the three-year-old image recognition startup in the past six months to more than $1.2 billion and tripling its valuation in under a year. Tiger Capital, Qualcomm Ventures and Hopu Capital also participated. The latest funding will go toward research and talent acquisition, SenseTime said in a statement, reports Fortune.com.

The company’s a big contributor to the world’s biggest system of surveillance: if you’ve ever been photographed with a Chinese-made phone or walked the streets of a Chinese city, chances are your face has been digitally crunched by SenseTime software built into more than 100 million mobile devices. The country is ramping up spending on surveillance as it cracks down hard on restive parts of the country, including Xinjiang.

A key focus for SenseTime is its internal talent development program, that seeks to cut its reliance on externally-trained AI developers as the industry hits a global crunch. It’s an effort that will become increasingly important as the U.S.—currently the source of many of the world leading computer science graduates—drafts limitations on how long Chinese students can stay in the country.

Aside from Alibaba, it also counts Temasek Holdings Pte and retailer Suning.com Co. as investors. It’s the largest, according to CB Insights, of a plethora of private AI outfits.

Fellow facial-recognition startup Megvii raised $460 million last year, while smaller niche players from Yitu to Malong Technologies have also won funding. A key partner, Hangzhou Hikvision Digital Technology, is one of the world’s biggest suppliers of security cameras and developing its own competing AI technology.