JPH0127544B

PURPOSE:To correct the large thermal diffusion in the horizontal diredtion, by way of a circuit by arranging the direction of extension of a fluorinated poly- vinylidene film so as to be parallel to the horizontal scanning direction of an electron beam. CONSTITUTION:The small thermal-image signal current from a pryoelectric type image-pickup tube 201 is amplified to a large signal through a preamplifier 202. The resolution of said thermal-image signal in the horizontal direction is reduced in comparison with that in the vertical direction because of the facial thermal diffusion on a fluorinated-polyvinylidene film. Therefore, the reduction of the resolution due to the thermal diffusion in the horizontal direction is corrected by a contour intensifying circuit (aperture compensation circuit) 203. Said aperture compensation circuit is constituted so that the output signal So is shown by the equation described in the separate part f(t): input signal, k: constant, gamma: frequency cycle corresponding to the compensation contour part , when an input signal f(t) is input. Therefore, the vignetting of the thermal image in the horizontal direction due to the thermal diffusion can be corrected, and a distinct thermal- image can be obtained.