Dirt detection method and device for camera cover

A detection device, comprising:

• a laser device disposed at an inner side of a camera cover and configured to transmit a laser pulse to a target object;
• an imaging sensor disposed at an inner side of the camera cover and configured to receive the laser pulse, form a first normal-frame image, a first detection-frame image, a second normal-frame image, and a second detection-frame image, obtain a first normal-frame grayscale value according to the first normal-frame image, obtain a first detection-frame grayscale value according to the first detection-frame image, obtain a second normal-frame grayscale value according to the second normal-frame image, and obtain a second detection-frame grayscale value according to the second detection-frame image;
• a processing module connected to the imaging sensor and configured to perform ratio operation on the first normal-frame grayscale value and the first detection-frame grayscale value to obtain a background grayscale image ratio, perform ratio operation on the second normal-frame grayscale value and the second detection-frame grayscale value to obtain a detection grayscale image ratio, and perform ratio operation on the detection grayscale image ratio and the background grayscale image ratio to obtain a grayscale ratio, where
• the processing module is further configured to determine whether a pixel in the second normal-frame image or the second detection-frame image is dirty according to a comparison result between the grayscale ratio and a dirt threshold, and determine whether a to-be-detected cover is in a dirty state according to the dirty pixel.