# US 9,751,300 B2 · Testing a printhead > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,751,300 B2 - Document ID: US9751300B2 - Status: Granted - Kind: B2 - Application number: 15/349,520 - Filed: 2016-11-11 - Published: 2017-03-02 - Granted: 2017-09-05 - Earliest claimed: 2016-11-11 - Assignees: Hewlett-Packard Development Company, L.P. - Applicants: Hewlett-Packard Development Company, L.P. - Inventors: Laura Portela Mata; David Soriano Fosas - Web page: https://patentgrep.com/patent/US9751300B2 ## CPC - B41J 2/0451: {for detecting failure, e.g. clogging, malfunctioning actuator} - B41J 2/04526: {controlling trajectory} - B41J 2/0456: {detecting drop size, volume or weight} - B41J 2/04561: {detecting presence or properties of a drop in flight} - B41J 2/04586: {controlling heads of a type not covered by groups B41J2/04575 - B41J2/04585, or of an undefined type} - 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 2/16585: {for paper-width or non-reciprocating print heads} - 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 19/20: Positive-feed character-spacing mechanisms (controlled by escapements B41J19/52) - B41J 29/393: Devices for controlling or analysing the entire machine {; Controlling or analysing mechanical parameters involving printing of test patterns} - G01J 1/0403: {Mechanical elements; Supports for optical elements; Scanning arrangements} - B41J: TYPEWRITERS; SELECTIVE PRINTING MECHANISMS, i.e. MECHANISMS PRINTING OTHERWISE THAN FROM A FORME; CORRECTION OF TYPOGRAPHICAL ERRORS - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) ## Abstract A system and method for testing printheads is disclosed. The system comprises an optical sensor mounted on a movable carriage. The optical sensor is moved past a nozzle to be tested on the printhead while the nozzle ejects ink. The output signal of the optical sensor can be used to determine when the trajectory of the ejected ink is improper. ## Claims ### Claim 1 A drop ejection device comprising: an optical sensor mounted on a movable carriage, the optical sensor comprising a light source and a light detector, the light source to emit a light beam towards the light detector; and a processor coupled to memory, the memory comprising computer readable instructions to test a nozzle of a head that, when executed by the processor, cause the device to: move the carriage, with the optical sensor, relative to the nozzle being tested such that a width of the light beam passes under the nozzle being tested from a leading side of the beam to a trailing side of the beam; fire multiple bursts of multiple drops from the nozzle being tested into the light beam whilst the carriage moves the light beam underneath the nozzle being tested; and analyze a signal from the light detector to evaluate operation of the nozzle being tested. ### Claim 2 (depends on 1) The device of claim 1, wherein the instruction, when executed, use the carriage to move at a constant velocity. ### Claim 3 (depends on 1) The device of claim 1, wherein the instructions, when executed, cause a gap in time between the bursts of multiple drops. ### Claim 4 (depends on 3) The device of claim 3, wherein the gap in time between the bursts of multiple drops is between 100 and 2000 microseconds. ### Claim 5 (depends on 1) The device of claim 1, wherein each burst of drops comprises 4-20 drops. ### Claim 6 (depends on 1) The device of claim 1, wherein the instructions, when executed, cause drops in a burst to be fired at a frequency between 6-24 kHz. ### Claim 7 (depends on 1) The device of claim 1, wherein the device comprises a printhead to eject ink and the carriage moves in a direction parallel with a direction in which a print medium moves. ### Claim 8 (depends on 1) The device of claim 1, wherein the device comprises a printhead to eject ink and the carriage moves in a direction perpendicular to a direction in which a print medium moves. ### Claim 9 (depends on 1) The device of claim 1, wherein the light beam has a diameter between 0.5 and 1 inches. ### Claim 10 (depends on 1) The device of claim 1, wherein the instructions cause the processor further to determine whether drops from the nozzle being tested have a desired trajectory based on the signal from the light detector. ### Claim 11 (depends on 10) The device of claim 10, wherein the instructions cause the processor to disable the nozzle being tested when the ejected drop trajectory is improper. ### Claim 12 A drop ejection device comprising: an optical sensor mounted on a movable carriage, the optical sensor comprising a light source and a light detector, the light source to emit a light beam towards the light detector; and a processor coupled to memory, the memory comprising computer readable instructions to test a nozzle of a head that, when executed by the processor, cause the device to: move the carriage, with the optical sensor, relative to the nozzle being tested such that a width of the light beam passes under the nozzle being tested from a leading side of the beam to a trailing side of the beam; fire a continuous stream of drops from the nozzle being tested into the light beam while the carriage moves the light beam underneath the nozzle being tested; and analyze a signal from the light detector to evaluate operation of the nozzle being tested. ### Claim 13 (depends on 12) The device of claim 12, wherein the instruction, when executed, cause the carriage to move at a constant velocity. ### Claim 14 (depends on 12) The device of claim 12, wherein the device comprises a printhead to eject ink and the carriage moves in a direction parallel with a direction in which the print medium moves. ### Claim 15 (depends on 12) The device of claim 12, wherein the device comprises a printhead to eject ink and the carriage moves in a direction perpendicular to a direction in which the print medium moves. ### Claim 16 (depends on 12) The device of claim 12, wherein the light beam has a diameter between 0.5 and 1 inches. ### Claim 17 (depends on 12) The device of claim 12, wherein the processor is further to determine whether drops from the nozzle being test have a desired trajectory based on the signal from the light detector. ### Claim 18 (depends on 17) The device of claim 17, wherein the processor is to disable the nozzle being tested when the ejected drop trajectory is improper.