Printing apparatus with missing dot testing
AssigneeSeiko Epson Corporation
InventorHironori Endo
Life of this patent
Estimating the term…
Abstract
The presence or absence of inoperative nozzles is detected by comparing a specific threshold with a time interval between successive detection pulses. The presence or absence of inoperative nozzles can thus be established without the use of information about the positional relation between the print head and the ink drop detection device, dispensing with the need to align the print head and the ink drop detection device with high accuracy.
Claims21
A printing apparatus, comprising:
- a print head including a nozzle row having a plurality of nozzles for ejecting ink drops, the plurality of nozzles being aligned in a direction of sub-scanning;
- an ink drop detector having a light emitter for emitting light and a light receiver for receiving the light emitted by the light emitter, the ink drop detector being configured to generate detection pulses in response to blockage of the light by the ink drops;
- a feed mechanism configured to move the print head and/or the ink drop detector in order for the print head and the ink drop detector to move relative to each other;
- a detection pulse analyzer capable of:
- (i) measuring a time interval of two consecutive detection pulses which are detected by the ink drop detector while the print head and the ink drop detector are relatively moving in a constant speed;
- (ii) judging that the two consecutive detection pulses are associated with a same nozzle if the time interval is less than a first threshold value, while judging that the two consecutive detection pulses are associated with two different nozzles if the time interval is greater than the first threshold value;
- and
- (iii) counting a number of operative nozzles capable of ejecting ink drops based on the judgment;
- and
- a nozzle condition determiner configured to determine presence of an inoperative nozzle incapable of ejecting ink drops if the number of operative nozzles is less than a number of test nozzles being subject to the ink drop detection.
A method for testing ejections of ink by a print head including a nozzle row having a plurality of nozzles for ejecting ink drops, the plurality of nozzles being aligned in a direction of sub-scanning, the method comprising:
- (a) generating light in a direction across paths of ink drops ejected from at least some of a plurality of nozzles subject to testing, while moving the print head and/or the light relative to each other at a constant speed;
- (b) generating detection pulses in response to blockage of the light by the ink drops;
- (c) measuring a time interval of two consecutive detection pulses which are detected by the ink drop detector while the print head and the ink drop detector are relatively moving in a constant speed;
- (d) judging that the two consecutive detection pulses are associated with a same nozzle if the time interval is less than a first threshold value, while judging that the two consecutive detection pulses are associated with two different nozzles if the time interval is greater than the first threshold value;
- (e) counting a number of operative nozzles capable of ejecting ink drops based on the judgment;
- and
- (f) determining presence of an inoperative nozzle incapable of ejecting ink drops if the number of operative nozzles is less than a number of test nozzles being subject to the ink drop detection.
A computer program product for causing a computer to test ejections of ink by a print head including a nozzle row having a plurality of nozzles for ejecting ink drops, the plurality of nozzles being aligned in a direction of sub-scanning, the computer program product comprising:
- a computer readable medium;
- and
- a computer program stored on the computer readable medium, the computer program comprising:
- a first program for causing the computer to control a generation of light in a direction across paths of ink drops ejected from at least some of a plurality of nozzles subject to testing, while moving the print head and/or the light relative to each other at a constant speed;
- a second program for causing the computer to control a generation of detection pulses in response to blockage of the light by the ink drops;
- a third program for causing the computer to measure a time interval of two consecutive detection pulses which are detected by the ink drop detector while the print head and the ink drop detector are relatively moving in a constant speed;
- a fourth program for causing the computer to judge that the two consecutive detection pulses are associated with a same nozzle if the time interval is less than a first threshold value, while judging that the two consecutive detection pulses are associated with two different nozzles if the time interval is greater than the first threshold value;
- a fifth program for causing the computer to a number of operative nozzles capable of ejecting ink drops based on the judgment;
- and
- a sixth program for causing the computer to determine presence of an inoperative nozzle incapable of ejecting ink drops if the number of operative nozzles is less than a number of test nozzles being subject to the ink drop detection.
Dependencies are inferred from the claim text.