| 摘要 |
PURPOSE:To improve an S/N ratio and thereby to detect the density of toner with high precision by reducing a diffused light component contained in a detected light, as much as possible. CONSTITUTION:Optical axes are regulated by providing a masking member 8 on a seal member surface 5 provided in front of pinholes 6 and 7. The position of the masking member 8 is defined by a projecting or recessed part formed in the seal member 5 beforehand and the masking member is provided in the part by coating or the like. The effect of refraction and diffusion in the seal member 5 is removed and thereby an S/N ratio can be improved. |
