SenseTime specialises in systems that analyse faces and images on an enormous scale. : BEIJINGSenseTime Group Ltd 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 Group Holding Ltd 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 start-up 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.