COLOR MARK SENSOR

PURPOSE:To make optimum spectroscopic sensitivity characteristic selectable while simplifying mechanical elements of the apparatus as a whole, by using a photo detection element of a tandem-structured photoelectric sensor as light receiving element for reflected light and light receiving element for comparison light. CONSTITUTION:Reflected lights from an object to be detected and a comparison light from a lamp are detected by a light receiving means 1. The light receiving means 1 has two photo detection elements 10 integrally formed in parallel, where a photoelectric sensor tandem construction 16 in which PIN-amorphous photoelectric sensors are stacked in two stages through a transparent electrode 12 is formed on a common glass substrate 11. Back electrodes 15 and 15' are formed in parallel on the construction 16 to draw photocurrent generated by the incidence of a comparison light or a reflected light. A reverse bias voltage is applied between the transparent electrode 12 and the back electrode 15' by a reverse bias voltage application means 2. The reverse bias voltage is selected and set easily from outside a color mark sensor, for example, using a variable resistor.