Swedish biometrics firm Fingerprints has seen its shares plunge by some 20% after a warning that revenues were being impacted by lower sensor prices.FPC said average selling prices for sensors have fallen by around 30 percent, versus a previous forecast of more than 20 percent. It said the industry had also turned more cautious ahead of Apple's iPhone X launch last week, dampening demand.”Fingerprints is currently experiencing a cautious market and one contributing factor is Apple's launch,” FPC said in a statement on Monday. It also blamed a weaker U.S. dollar.Fingerprints now expects third-quarter revenue of between 800 million and 840 million Swedish crowns ($100-105 million), compared to 823 million crowns in the second.Analysts were previously expecting revenue of almost 1.5 billion crowns, Thomson Reuters Eikon data shows. It had warned on profits three times since the end of 2016 and abandoned giving revenue forecasts.Apple's iPhone X includes hardware for facial recognition instead of a fingerprint sensor to unlock the phone. Some analysts say this is bad news for Fingerprints.