A method for error detection on an image sensor and an absolute position measuring system for a passenger transportation system

A method for error detection on an image sensor for an absolute position measuring system of a passenger transportation system using a light source, the method comprising steps of:

• illuminating a code of dark areas and light areas by the light source providing a first light intensity;
• acquiring, via the image sensor, a first measurement value by scanning the illuminated code;
• modifying the light source to provide a second light intensity illuminating the code;
• acquiring, via the image sensor, a second measurement value by scanning the code illuminated by the second light intensity;
• and
• evaluating a consistency condition using the second measurement value.

An absolute position measuring system for a passenger transportation system, the system comprising

• a code of dark areas and light areas;
• a light source illuminating the code;
• an image sensor scanning the code;
• and
• wherein the absolute position measuring system detects errors in the image sensor by executing steps of:
• illuminating the code with the light source providing a first light intensity;
• acquiring, via the image sensor, a first measurement value by scanning the code;
• modifying the light source to provide the second light intensity;
• acquiring, via the image sensor, a second measurement value by scanning the code;
• and
• evaluating a consistency condition using the second measurement value.