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Ink Drop Velocity Measurement via Coded Plates and Photodetectors

IP.com Disclosure Number: IPCOM000083056D
Original Publication Date: 1975-Mar-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Kuhn, L: AUTHOR [+4]

Abstract

In order to measure droplet velocity in a stream of periodic droplets emanating from an ink jet nozzle by making measurements over a moderately long distance, for example, a distance greater than the wavelength of the droplet stream, it is essential that means are employed for distinguishing any given droplet from neighboring droplets.

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Ink Drop Velocity Measurement via Coded Plates and Photodetectors

In order to measure droplet velocity in a stream of periodic droplets emanating from an ink jet nozzle by making measurements over a moderately long distance, for example, a distance greater than the wavelength of the droplet stream, it is essential that means are employed for distinguishing any given droplet from neighboring droplets.

In Fig. 1, a code plate 2 of alternate transmitting 4 and opaque absorbing regions 6 is placed in front of a photodetector 8. The photo-detector-code plate combination is coded to detect the passage of a droplet stream 10 in the direction of an arrow 12, by detecting the changes in light incident upon the photodetector-code plate combination from a light source, such as the light- emitting diode (LED) 14. The ink droplets modulate the light received at the photodetector by absorption.

In Fig. 2 the photodetector 8 and the code plate 2 are arranged in a similar manner to the system set forth in Fig. 1. A droplet stream 10 travels in the direction of the arrow and an LED 14 emits light on the droplet stream 10, which light is reflected and focussed by a lens 16 on the code plate 2 and the photodetector 8.

For a periodic code plate, the passage of an ink droplet across the photodetector-code plate aperture results in a periodic signal. The frequency generated is a function of the spatial period of the code plate and the velocity of the droplet. For a code plate with a sinusoidal absorption pattern of N lines/cm spatial frequency and for a droplet velocity of v cm/sec, the frequency detected by the photo-detector F = Nv sec/1/.

It is to be noted that neighboring droplets generate the same frequency, but with a different start phase to the signal.

In order to differentiate readily between the signals from neighboring droplets, the code pl...