Abstract: The present invention relates to an optical card reader that detects any relative inclination of the card by measuring the relative motion of the optical tracks themselves. The optical card reader comprises a card holding portion, an optical head having the ability follow data tracks on the optical card, and a detector that measures the angle of inclination of the optical card from a tracking signal generated from a one-dimensional relative movement of the card holder and the optical card.

Abstract: There is provided an optical card information recording/playing back apparatus comprising: an optical system for irradiating a light beam for reproducing recorded information onto information recording tracks of the optical card on which pit trains indicative of recording information are formed; a photo detector for receiving the reflected light from the optical card and outputting a photo sensing signal; a pit correspondence signal producing circuit for detecting a peak of the photo sensing signal and producing a pit correspondence signal which changes in correspondence to a pit position on the basis of the result of the peak detection; a frequency/voltage converter for converting a frequency of the pit correspondence signal to a voltage; and a discrimination signal producing circuit for comparing a voltage output of the frequency/voltage converter with a reference value and producing an information presence/absence discrimination signal.