PURPOSE: To prevent an uneven exposure by providing adjacently to a lens a correcting member constituted so that an opaque part is made dense in a part opposed to a central optical axis of a lens on a transparent base, and is made sparse as proceeding toward the circumference.

CONSTITUTION: As for an optical system B, a correcting member 9 is provided on the emitting side of a lens 6. As for the correcting member 9, a comparatively small spot 11 is printed so that it goes to dense in a part opposed to a central optical axis 6' of the lens 6, and goes to sparse toward the circumference, on a transparent base 10 such as a plastic plate, glass plate, etc., and the transmittivity of light velocity from the lens 6 is set so as to correct a COS fourth power rule. When an emitted luminous flux transmits through the correcting member 9, its transmission quantity is proportional to a light shielding factor of this luminous flux section, therefore, even if the intensity of illumination of an image forming surface drops as a view angle becomes large by the COS fourth power rule of the lens, its transmittivity and the drop of the intensity of illumination offset each other because the correcting member 9 has a reverse transmittivity, the intensity of illumination of the image forming surface is equalized, and the generation of an uneven intensity of illumination can be prevented.