| 摘要 |
PURPOSE:To improve reproducibility of the density of an original and to prevent deterioration in gradation when an original is copied or the like by providing a linearity correction means converting a digital signal into a digital image signal linear to an original reflectance to the reader. CONSTITUTION:The reader is provided with an A/D converter circuit 11 converting an analog output voltage from an image pickup element (CCD) into a digital signal and a linearity correction means 13 converting the digital signal into a digital image signal linear to the reflectance of the original. The linearity correction means 13 is interposed between a shading correction circuit 12 at the post-stage of the A/D converter circuit 11 and a logarithmic correction circuit 14 in the signal processing circuit. Then the linearity correction means 13 corrects a linearity error between the original reflectance and the digital signal or an analog output voltage of the image pickup element based on a preset gamma table. Thus, deterioration in the original density reproducibility of the reader due to reflection is improved and an image with high image quality is ensured for generation copies or the like. |
