US Patent 7751735 Image forming device with toner density detection

An image-forming device has an image-forming unit, a toner density detection unit, a reflective shutter, a storage unit, and a control unit. The control unit calculates a correction value for correcting the output value to control an image-forming unit according to the correction value. The image-forming unit forms a reference toner image on the image-carrying member. The toner density detection unit receives a reflected light beam from the reflective shutter positioned at the shielding position to generate a first output value, the first output value being stored in the storage unit. The toner density detection unit receives another reflected light beam from the reference toner image to generate a second output value when the reflective shutter is positioned at the retracted position, the second output value being stored in the storage unit. The control unit calculates a ratio of the second value and the first value and then calculates the correction value based on the ratio.