Abstract: Imaging methods, imaging device calibration methods, imaging devices, and hard imaging device sensor assemblies are described. According to one aspect, an imaging method includes forming a hard color image upon media using image data, the hard color image corresponding to the color image, and after the forming, sensing an optical characteristic of the hard color images at a plurality of different spatial locations of individual ones of the hard color images, and providing information regarding the optical characteristic at the different spatial locations of the hard color image after the sensing.

Abstract: A method and apparatus for monitoring marking liquid including a carrier liquid having solid particles therein. A transmitter emits an ultrasonic signal into the marking liquid. The ultrasonic signal is received by a receiver and processed by a controller to determine at least one of the temperature of the marking liquid and the concentration of solid particles in the marking liquid.

Abstract: Methods for measuring optical density are described. The color on an area is determined. Based on the color, at least a first illumination source is selected. The area is illuminated with the selected illumination source. Radiation is received from the area, and the received radiation is converted to a signal indicative of optical density.

Abstract: A method and apparatus for monitoring marking liquid including a carrier liquid having solid particles therein. A transmitter emits an ultrasonic signal into the marking liquid. The ultrasonic signal is received by a receiver and processed by a controller to determine at least one of the temperature of the marking liquid and the concentration of solid particles in the marking liquid.