In order to determine the quality of fuel in an auto-igniting internal combustion engine, a defined fuel amount is injected at defined crank shaft angles during a deceleration fuel shut-off phase of the internal combustion engine. According to this photosensitive material, it is possible to obtain a good image, which has a low residual potential and is free from fog. Additionally, the implant may be \u201cmatched\u201d to provide the implant with similar physical andor chemical properties as the host tissue.