A wearable device for detecting bio-signal, including an image sensor and a data processor. The image sensor is used for collecting light from a biological surface and generating a sensing image, and then analyzing the sensing surface to determine a bio-signal. The data processor is used for detecting the exposure information of the image sensor, such as a sensing period of the image sensor or a lighting period of a light source associated with the image sensor, and so as to determine if the wearable device is being worn correctly.一種偵測生理資訊之穿戴式裝置，包括一影像感測器以及一資料處理器。該影像感測器用以擷取一生物表面光線，並產生一感測影像，再分析該感測影像來計算一生理資訊。該資料處理器係偵測該影像感測器的曝光資訊，例如該影像感測器的收光時間或者與該影像感測器配合之一光源的打光時間，並根據該曝光資訊判斷該穿戴式裝置是否正確配戴。
