(57) A surface of a pyroelectric layer (1) of a latent image charge keeping medium (3)
is selectively heated by a thermal head (4) according to a video signal. In a heated
portion of the medium (3), there is collected electric charge to form an elecrtrostatic
latent image (17) on the surface of the pyroelectric layer (1). When the latent image
(17) is developed by a developer (7), a developing sleeve (10) is applied with an
appropriate bias voltage obtained according to temperatures of the thermal head (4),
the latent image charge keeping medium (3) and the apparatus sensed by temperature
sensors (21, 21a, 21b). This keeps the potential contrast between the latent image
(17) and the sleeve (10) to remain within a favorable range in any situation. Consequently,
even when the charge density of the latent image becomes excessive due to, for example,
heat accumulation of the thermal head (4), it is possible to prevent increase in the
recording density so as to suppress the foggy portion in the picture.
|
|
