Patent ID: 7676170

Claim:
A toner density detection apparatus comprising: a sensor unit configured to irradiate a pattern image for density measurement formed on an image carrier with light, split the light reflected by the pattern image into a first light component and a second light component, receive the first light component and the second light component, and output a first light reception signal and a second light reception signal; an analog/digital converter configured to convert, based on a first reference voltage for determining an upper limit of an analog signal to be converted, the first light reception signal output from the sensor unit into first digital data, and convert, based on a second reference voltage for determining an upper limit of an analog signal to be converted, second light reception signal output from the sensor unit into second digital data; a reference voltage generation unit configured to generate the first reference voltage and the second reference voltage; a density detection unit configured to detect a density of the pattern image based on the first digital data and the second digital data; and an adjusting unit configured to adjust the first reference voltage generated by the reference voltage generation unit so that the first digital data becomes a first predetermined value and adjust the second reference voltage generated by the reference voltage generation unit so that the second digital data becomes a second predetermined value, when a pattern image having a predetermined density is irradiated in an adjusting mode.