| 摘要 |
<p>PURPOSE: To ensure detection of the liquid drop of ink having a relatively small size by providing an optical sensor, amplifier band amplifier, first and second comparators. CONSTITUTION: The existence of ink liquid drop in an optical detection region between an LED and a photodiode 17 causes decrease in the electrical output of a diode 17. The output of a mutual conductance amplifier 21 decreases according to decrease in the output of the diode 17. The output of a band amplifier 25 becomes a voltage signal to decrease the oscillation level according to decrease in the output of the diode 17. The outputs of digital comparators 41, 42 are equalized over a plurality of series ink liquid drops and the determination whether a print head nozzle injects ink drops or not can be made. For each minimum liquid drop size, separate reference circuits 31, 32 and comparator circuits 41, 42 are arranged, whereby an efficient detection of liquid drop of larger minimum liquid drop size can be made by one liquid drop. The respective reference voltages V1, V2 are finely synchronized with a specified minimum liquid drop so that the reliability is improved.</p> |
