LIGHT BEAM IRRADIATING DEVICE

摘要

PURPOSE:To improve the resolution of a character picture and to reproduce a picture with intermediate gradation by changing at least the light beam irradia tion pulse width or light beam spot diameter in comparison with and in corre spondence to a density pattern table. CONSTITUTION:The density level of each picture element of a picture signal read by an image sensor is digitized and the result enters a shift memory 6. The density level under irradiation is compared with a density pattern table and covnerted by using a comparison circuit 7 comparing the density level of the picture element under irradiation in the shift memory 6 with that of the adjacent picture element. A semiconductor laser 1 is driven by a pulse width proportional to the density level converted by a modulation circuit 8. When adjacent picture element density levels are difference in the comparison circuit 7, the start time of a drive pulse is decided by a control circuit 9 so as to be in contact with a picture element having a larger density level. The shape of the laser beam spot formed by the photosensitive body 4 is formed shorter in the width in the scanning direction and longer (shape 5) in the direction orthogonal to the scanning direction to make the pulse width modulation effective to the recording picture.