FIELD: safety.
SUBSTANCE: invention relates to a method for checking a specified security feature of a value document. Method for checking a specified security feature of a value document, preferably a watermark, wherein there are captured pixel data, which describe, spatially resolved with a specified optical spatial resolution, an optical image, there are captured ultrasound data which describe an ultrasonic property of value document at least in security-feature region, spatially resolved with a specified ultrasonic spatial resolution, ultrasonic spatial resolution being lower than optical spatial resolution, from pixel data there are established first reduced-resolution pixel data for reduced-resolution pixels of a first reduced-resolution image which describe a reduced-resolution optical image.
EFFECT: technical result is improved reliability of examining a value document.
20 cl, 12 dwg
