Abstract: A reflection densitometer includes a light source and a photodetector having an output which has a signal component characteristic of the amount of reflected light received from a surface to be measured and a noise component. The noise component of the output is isolated in time by switching the light source on and off so as to create alternating first and second time periods during which the output of the photodetector is characteristic of only the noise component and in which the output of the photodetector is characteristic of both the signal component plus the noise component, respectively. The output of the photodetector during the second time period is subtracted from the output during the first time period to obtain a signal characteristic of only the output of the photodetector characteristic of relected light received.

Abstract: A dry toner image is embedded in a thermoplastic layer on a receiving sheet by pressing a ferrotyping web against the image in the presence of sufficient heat to soften the layer. Preferably, the layer is preheated and the web and image are pressed together by a pair of hard rollers to a pressure in excess of 100 pounds per square inch.A curl preventing layer opposite thermoplastic layer does not offset on a backing roller because it has a melting point above the temperature of the process.

Abstract: Control over the electrostatographic process is provided by adjusting the toner charge-to-mass ratio in response to changes in toner contrast. An electrostatographic reproduction machine produces a signal having a value characteristic of the toned density of the developed image. Using the signal, the charge-to-mass ratio of the toner is adjusted. In a preferred embodiment, the signal is produced by comparing the toned density of the developed image to a reference value, and charge-to-mass is adjusted by directing an ion cloud over the toner particles.

Abstract: In electrostatographic apparatus, the ratio of toner particle electrostatic charge-to-toner particle mass and the development rate are determined by providing a piezo device positioned to interact with toner particles. The device is periodically electrically biased to attract toner particles, and the frequency shift of the piezo device due to the mass of attracted toner particles is detected. The electrostatic charge buildup on the electrode due to the attracted toner particles is detected to determine the mass of toner. The potential on the device may be changed periodically from a potential which attracts toner to a potential which repels toner to clean the device.

Abstract: Apparatus is disclosed for controlling the charge-to-mass ratio of developed electrostatic images. An electrostatographic reproduction machine for developing an electrostatic latent image with charge toner particles produces a control signal characteristic of the ratio of toner partical electrostatic charge to the toner particle mass, and the charge-to-mass ratio is adjusted in response to the control signal. The control signal is produced by comparing the ratio of toner particle electrostatic charge to the toner particle mass of a toned test patch. The ratio is adjusted by means of ions directed to the toner particles. The ion source may be capable of producing positive and negative ions, and may be a corona charger.

Abstract: Apparatus and method for controlling the development rate of an electrostatic photocopying machine. An electrode plate is positioned adjacent to the toning brush to form a capacitive circuit in which a portion of the dielectric is the toner mixture used in developing images in the machine. Reversing polarities are applied to the electrode plate to alternately make it attract and repel toner. During the attracting or developing polarity, the transient behavior of the toning current is detected and this transient response is used to determine the development rate of the apparatus. In the specific embodiment described, the transient characteristic detected is the time required for the charging current to decay to a predetermined value.