Optical monitoring device

An optical monitoring system for monitoring surroundings, comprising an optical monitoring apparatus, having a visual or scanning field, which is captured by a lens, and a protection panel (12;

• 14;
• 114;
• 314;
• 112;
• 218;
• 318) which protects the lens from precipitation and covers at least the visual or scanning field of the monitoring apparatus, characterized in that the protection panel (12;
• 14;
• 114, 214;
• 314;
• 112;
• 218;
• 318) is acoustically coupled to at least one ultrasonic transducer (10;
• 10 a-j;
• 1611;
• 1612;
• 1711-1718), the at least one transducer (10;
• 10 a-j, 1611;
• 1612;
• 1711-1718) is actuated by a frequency-modulated signal in a first mode and actuated by an amplitude-modulated signal in a second mode and actuated by a phase-modulated signal in a third mode wherein each mode has a time-variable modulation.