| 摘要 |
PURPOSE:To compensate the shading according to the 4th power of cosine of a lens in an excellent way, by multiplying a sinusoidal wave signal synchronized with the storage time of a CCD with a photoelectrically converted output from the CCD. CONSTITUTION:An image illuminance E is proportional to the 4th power of cosine of an angle theta of an incident ray to an optical axis (E=kcos<4>theta). The reflected light from an original 4 is shrinked at a lens 5, projected to a CCDb and photoelectrically converted. A rectangular wave signal generated from a rectangular wave signal generator 8 synchronized with the storage time of the CCD is inputted to a band pass filter 9 using the reciprocal of the storage time as a center frequency to obtain a sinusoidal signal synchronized with the storage time of the CCD. Based on this sinusoidal wave signal, the output of a picture signal processing circuit 7 is multiplied with the picture signal at a multiplication processing circuit 10, allowing to compensate shading. |
