Method for determining a state of a driver monitoring device and driver monitoring device

A method for determining a state of a driver monitoring device, the device comprising an illumination device for illuminating an interior of a vehicle, a diffuser (120) arranged in a beam path of the illumination device in the correct state of the driver monitoring device for scattering a light emitted by the illumination device, and an image capturing device for capturing an image of the interior, the method comprising:

• illuminating, by the illumination device, the interior, and generating at least one first image of at least one section of the interior,
• wherein said first image being based on an image of the interior which is illuminated by means of the illumination device,
• wherein said image is captured by the image capturing device;
• dividing the at least one first image into a left upper image section, a right upper image section, a left middle image section, a right middle image section, a left lower image section and a right lower image section;
• determining a maximum intensity of pixels of a first group of image sections of the at least one first image,
• wherein said first group comprising the left middle image section and the right middle image section;
• and
• determining an average intensity of a second group of image sections of the at least one first image,
• wherein said second group comprising the left upper image section, the right upper image section and the right lower image section or the left upper image section, the right upper image section and the left lower image section;
• determining a difference in illumination of the at least one first image by dividing the maximum intensity of the first group of image sections of the at least one first image by the mean intensity of the second group of image sections of the at least one first image;
• and
• determining that the diffuser is functional and properly arranged in the beam path of the illumination device and activating the illumination device for driver monitoring if the difference in illumination of the at least one first image is smaller than a lower threshold value, or
• determining that the diffuser is not functional and properly arranged in the beam path of the illumination device and deactivating the illumination device if the difference in illumination is greater than an upper threshold value.