| 摘要 |
PROBLEM TO BE SOLVED: To enable suppression of variation in detection accuracy due to position deviation when an element is surface-mounted and achieving reduction in size.SOLUTION: There is provided a toner density sensor 11 which comprises: a light-emitting element 12 means for emitting light; light-receiving elements 13 and 14 which receive the reflected light emitted from the light-emitting element 12 and reflected by a detection target; an optical path having an irradiation path 21 which is formed along a surface of a printed circuit board 15 on which the light-receiving elements are surface-mounted and passes light applied from the light-emitting element 12 and light receiving paths 22 and 23 for passing the reflection light; and diaphragm parts 25 and 26 which are formed in the optical path and partially narrow the optical path. The diaphragm parts 25 and 26 are separated into upper side parts 25a and 26a of the diaphragm parts and lower side parts 25b and 26b of the diaphragm parts, the diaphragm parts 25 and 26 being disposed in an upper case 17 for covering a surface of the printed circuit board 15 and a lower case 18 for covering a rear surface of the printed circuit board 15. A through hole 31 for protruding the lower side parts 25b and 26b of the diaphragm parts from the rear surface to the surface is formed on the printed circuit board 15. |
