# US 5,708,916 A · Developed mass per unit area controller without using electrostatic measurements > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,708,916 A - Document ID: US5708916A - Status: Granted - Kind: A - Application number: 08/757,057 - Filed: 1996-11-26 - Granted: 1998-01-13 - Earliest claimed: 1996-11-26 - Assignees: Xerox Corporation - Inventors: Lingappa K. Mestha - Web page: https://patentgrep.com/patent/US5708916A ## CPC - G03G 15/5041: {Detecting a toner image, e.g. density, toner coverage, using a test patch (G03G15/553 takes precedence)} - G03G 2215/00042: Optical detection - G03G 2215/00063: Colour - G03G: ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY ## Abstract An electrostatographic printing machine having an imaging system for projecting and developing images on an imaging member. A process control loop includes a sensor to measure developed mass per unit area on at least three test patches on the imaging member including high area coverage, low area coverage, and mid tone coverage. A comparator responds to the sensor measurements and to developed mass per unit area setpoints to provide error signals. A control unit responds to the error signals to adjust projecting, developing, and imaging member subsystems. ## Claims ### Claim 1 In an imaging system for projecting and developing images on an imaging member, a process control loop comprising; a sensor to measure developed mass per unit area, the sensor measuring at least three test patches on the imaging member including high area coverage, low area coverage, and mid tone coverage, a control unit to process the error signals to actuate projecting, developing, and imaging member subsystems, the control including stored nominal actuator values, an integrator, and a compensator, the compensator responding to the integrator and nominal actuator values. ### Claim 2 (depends on 1) The process control loop of claim 1 wherein the projecting subsystem actuator is raster output scanner power. ### Claim 3 (depends on 1) The process control loop of claim 1 wherein the developing subsystem actuator is bias voltage. ### Claim 4 (depends on 1) The process control loop of claim 1 wherein the imaging member subsystem actuator is charting voltage. ### Claim 5 (depends on 1) The process control loop of claim 1 wherein high area coverage is approximately 90% to 100%, low area coverage is approximately 0 to 20% and mid tone area coverage is approximately 50%. ### Claim 6 (depends on 1) The process control loop of claim 1 wherein the control unit is a single multiple-input multiple-output controller. ### Claim 7 An electrostatographic printing machine having an imaging member, a charging device for charging the imaging member, an image projecting device, and a developer device for apply toner to the imaging member, a control having control parameters comprising: a sensor to sample developed toner mass per unit area on the imaging member and provide signals, a first actuator signal to enable the charging device, a second actuator signal to enable the developer device, a control responsive to the sensor signals to adjust both the first actuator signal to enable the charging device and the second actuator signal to enable the developer device, the control including stored nominal actuator values, an integrator, and a compensator, the compensator responding to the integrator and nominal actuator values. ### Claim 8 (depends on 7) The electrostatographic printing machine of claim 7 wherein the image projecting device is a raster output scanner and including a third actuator signal to enable the raster output scanner. ### Claim 9 (depends on 8) The electrostatographic printing machine of claim 8 wherein the integrator is responsive to the sensor signals to adjust the third actuator signal to enable the raster output scanner. ### Claim 10 (depends on 7) The electrostatographic printing machine of claim 7 wherein the control includes a gain matrix providing adjusted first and second actuator signals in response to sensor signals. ### Claim 11 (depends on 10) The electrostatographic printing machine of claim 10 wherein the gain matrix is defined by a mathematical expression. ### Claim 12 (depends on 7) The electrostatographic printing machine of claim 7 wherein the sensor measures low, medium, and high developed toner mass per unit area samples on the imaging member. ### Claim 13 (depends on 7) The electrostatographic printing machine of claim 7 wherein the compensator is a summing node. ### Claim 14 An electrostatographic printing machine having an imaging member, a charging device for charging the imaging member, an image projecting device, and a developer device for apply toner to the imaging member, a control having control parameters comprising: a sensor to sample developed toner mass per unit area on the imaging member and provide signals, a first actuator signal to enable the charging device, a second actuator signal to enable the developer device, a source of reference signals, a comparator responsive to the reference signals and the sensor signals to provide error signals, and a control including an integrator and summing node responsive to the error signals to adjust both the first actuator signal to enable the charging device and the second actuator signal to enable the developer device. ### Claim 15 (depends on 14) The electrostatographic printing machine of claim 14 wherein the image projecting device is a raster output scanner and including a third actuator signal to enable the raster output scanner. ### Claim 16 (depends on 15) The electrostatographic printing machine of claim 15 wherein the control is responsive to error signals to adjust the third actuator signal to enable the raster output scanner. ### Claim 17 (depends on 14) The electrostatographic printing machine of claim 14 wherein the control matrix is a gain matrix defining imaging member, image projecting device, and developer device interaction. ### Claim 18 (depends on 14) The electrostatographic printing machine of claim 14 wherein the sensor measures low, medium, and high developed toner mass per unit area samples on the imaging member. ### Claim 19 (depends on 14) The electrostatographic printing machine of claim 14 wherein the summing node is responsive to nominal actuator values.