Provided are an optical correcting system which can form a linear image or illuminating light having a substantially uniform light intensity distribution without reducing the efficiency of use of light, and an exposure head which can perform excellent exposure by using the linear image or the illuminating light. Light flux from a light source is collimated by the function of a collimator lens, and the collimated light flux enters into an optical correcting system for correcting light intensity distribution. The optical correcting system for correcting light intensity distribution changes the width of the light flux at the exit position at which each collimated light flux exits so that the light intensity distribution of a linear image is uniform when the collimated light flux is formed into the linear image. A change of the widths of the light flux allows utilizing the light flux at the midsection generally having a high light intensity distribution for the peripheral having an insufficient light intensity, thereby uniformalizing the light intensity distribution of the linear image without reducing the efficiency of use of light as a whole.