an exposure apparatus for image formation uses power control means provided to a laser driver for controlling exposure energy and accordingly forming an image . specifically , exposure energy is varied depending on an isolated - dot pattern and an isolated - line pattern by changing the pulse height of a drive pulse for each dot . both of the isolated - line and isolated - dot patterns of a high resolution can thus be reproduced with a high image quality without increase of cost due to requirements for accuracy in processing and positioning of a lens and without decrease of life of a photoreceptor due to a decreased thickness of its photosensitive layer .