Incremental printing of symbolic information – Ink jet – Medium and processing means
Reexamination Certificate
2002-11-22
2004-04-27
Meier, Stephen D. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Medium and processing means
C347S019000, C347S081000
Reexamination Certificate
active
06726318
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a device for detecting microscopic droplets which detects a jetting condition of droplets jetted from a nozzle that jets microscopic droplets, and an ink-jet recording apparatus using the same.
In an ink-jet recording apparatus which jets microscopic droplets from a nozzle provided on a recording head on a recording medium for image recording, a jetting condition of ink is detected by the detection of an absence/presence of jetting of an ink droplet (hereinafter referred to as a droplet) from each nozzle, or by the detection of a flying speed of the jetted droplet, before the performance of an image recording, however, since the jetted droplet becomes further microscopic by the improvement of image quality in terms of a printing accuracy in the present years, the microscopic droplet not greater than 4 pico-liter must be detected, today.
In the past, in order to detect the jetting condition of the droplet, a detecting section that is composed of a light emitting element and a light receiving element is provided to cross a traveling course of the droplet, and a shadow against the detecting light representing a piece of droplet passing through between the light emitting element and the light receiving element on the optical axis is received by the light receiving element, and then, a change of amount of light caused by the shadow is detected and amplified, and thereby, the presence of the ink-jet from the nozzle is detected, in the case of detecting the presence/absence of the jetting, for example. However, due to the tendency that the droplet becomes more microscopic in the future and the image quality becomes higher, the shadow of the more microscopic droplet in a size of about ten-odd &mgr;m must be detected and its faint signal must be amplified, which causes the fear that correct detection will become difficult due to the deterioration of S/N ratio.
For the measure, a laser diode is used for a light source of the light emitting element so that the light amount per unit area becomes large, or a lens is dropped down when an LED is used for the light source so that the detecting area is stopped down as far as possible, and thereby, it is conceivable that the S/N ratio is improved by making the shadow of the droplet caught by the detecting section to be larger relatively, compared to the detecting area. However, since a carriage moves in the scanning direction, an accuracy for stopping the recording head is requested more and more severely so that the droplet jetted from the nozzle of the recording head may pass through on the optical axis between the light emitting element and the light receiving element, in order to stop the recording head accurately. To improve the stopping accuracy, the higher performance of a motor driving servo including the detection of the position is requested, which causes not only the cost increase but also the deterioration of the total detecting accuracy, caused by the malfunction of the detection owing to the shift of the stopping position.
With the foregoing as a background, there has been proposed a technology wherein the area covered by the droplet in the detecting area that is detectable by the light receiving element is made to be larger so that the microscopic droplet can be detected (Patent document 1), by the manner that a jetting interval in detecting the jetting of the droplet is established to be shorter than the jetting interval in operating the normal printing, or by the manner that a jetting amount of the droplet per unit time in detecting the jetting of the droplet is established to be larger than the jetting amount of the droplet per unit time in operating the normal printing.
(Patent document 1) Japanese TOKKAIHEI 11-78051
However, when the droplets are jetted continuously, there is a following problem, which clears that an appropriate detection cannot be conducted. That is, when the droplet pass through the detection area of the light receiving element, though the change of the amount of light received by the light receiving element is detected, there occurs the condition that the amount of light when the droplets are passing through hardly changes in the technology described in the above-mentioned patent document. Due to this, even if the output signal from the light receiving element is amplified, it is difficult to select only the signal of the changed value of the light amount from the noise component, causing a problem of miss detection, being impossible to obtain a detecting signal having better S/N ratio.
Further, since the droplet is detected optically by the light receiving element, it often comes under the influence of disturbance light in the course of the detecting operation, and S/N ratio of the detected signal is declined by this influence, causing a problem of miss detection.
Still further, there is a case that the light amount detected by the light receiving element varies depending on the type of the droplet such as the difference of color of ink. In such a case, there is a fear of miss detection due to the difference of the sensitivity of the light receiving element for each type of the ink, accordingly, it is desired that the sensitivity is easily adjustable.
SUMMARY OF THE INVENTION
Accordingly, the first subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can perform, with high S/N ratio, the detection of the jetting condition of the droplets from the nozzle, by discriminating clearly the optical detection and non-detection of the droplets jetted from the nozzle.
Further, the second subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can perform, with high S/N ratio, the detection of the jetting condition of the droplets from the nozzle without coming under the influence of the environmental noise such as the disturbance light.
Still further, the third subject of the present invention is to provide a microscopic droplet detecting device and an ink-jet recording apparatus which can always detect the droplets with the stable sensitivity, independently of the type of the droplets.
The above-mentioned matters are solved by the following Structures.
Structure 1 is a microscopic droplet detecting device for detecting the passage of droplets jetted from a nozzle, having therein, a droplet detecting section in which a light emitting element and a light receiving element are arranged to cross over a traveling course of the droplet jetted from the nozzle and the plural droplets can exist in the distance in the traveling direction of the droplets within the detecting limit of the detecting light emitted from the light emitting element to the light receiving element, a jet control section for controlling a jetting of a group of the droplets composed of the plural and continuous droplets which are jetted from the nozzle, and a jetting condition detecting section for detecting the jetting condition of the droplets from the nozzle, based on the output signal which is obtained by detecting the droplets group controlled by the jet control section by the droplet detecting section, wherein the jet controlling section provides a suspension period in which the droplet is not jetted between a preceding group of serial droplets and a following group of serial droplets which are measured by the droplet detecting section, and wherein when the suspension period is represented by &bgr;, a distance along the traveling direction of the group of serial droplets (hereinafter referred to as the droplets group) within the detecting limit of the droplet detecting section is represented by L (m), and a speed of the droplets for passing through the detecting limit of the droplet detecting section is represented by V (m/sec), the condition expressed by &bgr;≧L/V is satisfied.
In Structure 1, by providing the suspension period &bgr; so as to satisfy the above-mentioned condition, the distance between the droplets group having passed thr
Do An H.
Frishauf Holtz Goodman & Chick P.C.
Konica Corporation
Meier Stephen D.
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