# US 8,770,707 B2 · Drop detector assembly and method > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,770,707 B2 - Document ID: US8770707B2 - Status: Granted - Kind: B2 - Application number: 13/818,341 - Filed: 2010-09-02 - Published: 2013-07-18 - Granted: 2014-07-08 - Earliest claimed: 2010-09-02 - Assignees: Hewlett-Packard Development Company, L.P. - Applicants: Alexander Govyadinov; Andrew L. Van Brocklin; Donald W. Schulte; Terry McMahon - Inventors: Alexander Govyadinov; Andrew L. Van Brocklin; Donald W. Schulte; Terry McMahon - Web page: https://patentgrep.com/patent/US8770707B2 ## CPC - B41J 2/125: Sensors, e.g. deflection sensors {(nozzle clogging detection for cleaning reasons B41J2/16579; detection for compensation for failed nozzles B41J2/2139)} - B41J 2/2142: {Detection of malfunctioning nozzles (generating single droplets or particles on demand by pressure, e.g. electromechanical transducers B41J2/045, B41J2/05; jet deflection sensors B41J2/125; for cleaning purposes B41J2/16579)} - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS ## Abstract A drop detector assembly includes an ejection element formed on a substrate to eject a fluid drop, and a light detector formed on the substrate to detect light scattered off of the fluid drop. A fluid drop ejected from a nozzle formed in a transparent nozzle plate scatters light that is detected through the transparent nozzle plate. ## Claims ### Claim 1 A drop detector assembly comprising: an ejection element formed on a substrate to eject a fluid drop; a transparent nozzle plate; and a light detector formed on the substrate to detect light, through the transparent nozzle plate, scattered off of the fluid drop as the fluid drop passes through a light beam. ### Claim 2 (depends on 1) A drop detector assembly as in claim 1, further comprising a detector circuit formed on the substrate to provide a signal associated with the detected light, the signal indicating a condition of the ejected fluid drop. ### Claim 3 (depends on 2) A drop detector assembly as in claim 2, further comprising a controller to control the ejection element, determine the condition of the ejected fluid drop based on the signal, and correlate the condition with the ejection element. ### Claim 4 (depends on 2) A drop detector assembly as in claim 2, wherein the signal is current and the detector circuit is configured to integrate the current and transform the current into voltage, the drop detector assembly further comprising: a timing generator to control detector circuit integration time and transfer of the voltage to an analog to digital convertor (ADC) via an analog bus; and the ADC to convert the voltage into a digital signal. ### Claim 5 (depends on 1) A drop detector assembly as in claim 1, further comprising a light source to project a light beam to scatter light off of the fluid drop. ### Claim 6 (depends on 5) A drop detector assembly as in claim 5, wherein the light detector is positioned between the drop ejection element and the light source. ### Claim 7 A method of detecting fluid drop ejections in a fluid ejection device comprising: ejecting a fluid drop through a light beam from a nozzle formed in a transparent nozzle plate; and detecting through the transparent nozzle plate, scattered light reflected off of the fluid drop. ### Claim 8 (depends on 7) A method as in claim 7, further comprising generating a drop indicator signal indicating the condition of the fluid drop. ### Claim 9 (depends on 8) A method as in claim 8, further comprising: detecting light when a fluid drop is not ejected; generating a dark value signal based on light detected when a fluid drop is not ejected; finding a difference between the drop indicator signal and the dark value signal; and determining if the nozzle is functioning properly based on the difference. ### Claim 10 (depends on 7) A method as in claim 7, wherein detecting scattered light comprises using a light detector disposed on a substrate underlying the transparent nozzle plate. ### Claim 11 (depends on 10) A method as in claim 10, further comprising transforming current from the detector into voltage. ### Claim 12 (depends on 7) A method as in claim 7, wherein ejecting a fluid drop comprises actuating an ejection element disposed on a substrate underlying the transparent nozzle plate. ### Claim 13 (depends on 7) A method as in claim 7, wherein detecting comprises: resetting a detector circuit prior to the ejecting a fluid drop; integrating current generated by the light detector from the scattered light; transforming the current into a voltage; converting the voltage to a drop indicator signal through an analog to digital convertor; and transmitting the drop indicator signal to a printer controller. ### Claim 14 A drop detection system comprising: a fluid ejection assembly having a fluid drop ejection element integrated on a die substrate; a transparent nozzle plate; a light detector integrated on the die substrate; and an electronic controller to control the ejection element to eject a fluid drop and to control the light detector to detect light, through the transparent nozzle plate, scattered off of the fluid drop as the fluid drop passes through a light beam.