Method and apparatus for controlling the formation and shape of droplets in an ink jet stream

Claim 2

In an ink jet printing system, a method of controlling the formation of droplets in an ink jet stream, said method comprising the steps of: illuminating said ink jet stream in a region where the stream has yet to break up to form droplets; sensing the surface wave profile of the illuminated ink jet stream; responding to the sensed surface wave profile for providing a first signal at a frequency F; responding to the sensed surface wave profile for providing at least a second signal at a freuqency nF, where n is an integer ≧2; and combining said first and second signals to provide a control signal which is used to excite said ink jet stream, which excitation controls the formation of droplets.

Claim 3

In an ink jet printing system, a method of controlling the formation of droplets in an ink jet stream, said method comprising the steps of: illuminating the continuous portion of said ink jet stream with a source of radiant energy; sensing the surface wave profile of the illuminated ink jet stream; responding to the sensed surface wave profile for providing a first signal at the fundamental frequency F of the ink jet stream; responding to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2; and summing said first and second signals to provide a control signal which is used to excite said ink jet stream for controlling the formation of droplets.

Claim 4

In an ink jet printing system, a method of controlling the formation of droplets in an ink jet stream, said method comprising the steps of: illuminating the continuous portion of said ink jet stream with a source of radiant energy; sensing the surface wave profile of the illuminated ink jet stream; responding to the sensed surface wave profile for providing a first signal at the fundamental frequency F of the ink jet stream; responding to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2; and summing said first and second signals to provide a control signal which is used to excite said ink jet stream for controlling the formation of droplets.

Claim 5

The method of claim 2, wherein said radiant energy source comprises a laser.

Claim 6

In an ink jet printing system, apparatus for controlling the shape of droplets at break-off in an ink jet stream, said apparatus comprising: means for illuminating said ink jet stream in a region where the stream has yet to break up to form droplets; means for sensing the surface wave profile of the illuminated ink jet stream; means responsive to the sensed surface wave profile for providing a first signal at a frequency F, the amplitude of which is a function of the sensed surface wave profile; means responsive to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2, with the amplitude and phase of said second signal being a function of the sensed surface wave profile; and means for combining said first and second signals to provide a control signal which is used to excite said ink jet stream, for controlling the shape of droplets at break-off from said ink jet stream.

Claim 7

In an ink jet printing system, apparatus for controlling the shape of droplets at break-off in an ink jet stream, said apparatus comprising: means for illuminating said ink jet stream in a region where the stream has yet to break up to form droplets; means for sensing the surface wave profile of the illuminated ink jet stream; means responsive to the sensed surface wave profile for providing a first signal at a frequency F, the amplitude of which is a function of the sensed surface wave profile; means responsive to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2, with the amplitude and phase of said second signal being a function of the sensed surface wave profile; and means for combining said first and second signals to provide a control signal which is used to excite said ink jet stream, for controlling the shape of droplets at break-off from said ink jet stream.

Claim 8

In an ink jet printing system apparatus for controlling the shape of the droplets at break-off in an ink jet stream, said apparatus comprising: means for illuminating the continuous portion of said ink jet stream with a source of radiant energy; means for sensing the surface wave profile of the illuminated ink jet stream; means responsive to the sensed surface wave profile for providing a first signal at the fundamental frequency F of the ink jet stream, the amplitude of which is a function of the sensed surface wave profile; means responsive to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2, with the amplitude and phase of said second signal being a function of the sensed surface wave profile; and means for summing said first and second signals to provide a control signal which is used to excite said ink jet stream for controlling the shape of droplets at break-off from said ink jet stream.

Claim 9

In an ink jet printing system apparatus for controlling the shape of the droplets at break-off in an ink jet stream, said apparatus comprising: means for illuminating the continuous portion of said ink jet stream with a source of radiant energy; means for sensing the surface wave profile of the illuminated ink jet stream; means responsive to the sensed surface wave profile for providing a first signal at the fundamental frequency F of the ink jet stream, the amplitude of which is a function of the sensed surface wave profile; means responsive to the sensed surface wave profile for providing at least a second signal at a frequency nF, where n is an integer ≧2, with the amplitude and phase of said second signal being a function of the sensed surface wave profile; and means for summing said first and second signals to provide a control signal which is used to excite said ink jet stream for controlling the shape of droplets at break-off from said ink jet stream.

Claim 10

The apparatus of claim 5, wherein said radiant energy source comprises a laser.

Claim 11

In an ink jet printing system, apparatus for controlling the shape of droplets at the point of break-off in an ink jet stream, said apparatus comprising: a source of ink which emits an ink jet stream; perturbation means for perturbing said source of ink for causing the formation droplets; means for illuminating the continuous portion of said ink jet stream with a source of radiant energy; means for sensing the surface wave profile of the illuminated ink jet stream, and for converting same to an electrical signal containing the frequency components of the sensed radiant energy; a first means responsive to said electrical signal for providing a first signal at the fundamental frequency F of the ink jet stream, the amplitude of which is a function of the sensed fundamental frequency component of the sensed surface wave profile; a second means responsive to said electrical signal for providing at least a second signal at a frequency nF, where n is ≧2, with the amplitude and phase of said second signal being a function of the sensed fundamental and nth frequency of the sensed surface wave profile; and means for summing said first and second signals to provide a control signal which is applied to said perturbation means for controlling the perturbation of said ink jet stream and the shape of droplets at the point of break-off from said ink jet stream.

Claim 12

In an ink jet printing system, apparatus for controlling the shape of droplets at the point of break-off in an ink jet stream, said apparatus comprising: a source of ink which emits an ink jet stream; perturbation means for perturbing said source of ink for causing the formation droplets; means for illuminating the continuous portion of said ink jet stream with a source of radiant energy; means for sensing the surface wave profile of the illuminated ink jet stream, and for converting same to an electrical signal containing the frequency components of the sensed radiant energy; a first means responsive to said electrical signal for providing a first signal at the fundamental frequency F of the ink jet stream, the amplitude of which is a function of the sensed fundamental frequency component of the sensed surface wave profile; a second means responsive to said electrical signal for providing at least a second signal at a frequency nF, where n is ≧2, with the amplitude and phase of said second signal being a function of the sensed fundamental and nth frequency of the sensed surface wave profile; and means for summing said first and second signals to provide a control signal which is applied to said perturbation means for controlling the perturbation of said ink jet stream and the shape of droplets at the point of break-off from said ink jet stream.

Claim 13

The combination claimed in claim 7, wherein said means for illuminating comprises a laser.

Claim 14

The combination claimed in claim 7, wherein said first mean comprises: a bandpass filter for passing a sinusoidal signal at the fundamental frequency F; a rectifier for rectifying said sinusoidal signal; an integrator for integrating the rectified sinusoidal signal for providing a direct current signal proportional to the amplitude of the sinusoidal signal; a comparator for comparing said direct current signal with a reference signal; and means for providing said first signal at the fundamental frequency F in response to the comparison.

Claim 15

The combination claimed in claim 9, wherein said first means comprises: a bandpass filter for passing a sinusoidal signal at the frequency nF; a rectifier for rectifying said sinusoidal signal; a first integrator for integrating the rectified sinusoidal signal for providing a first direct current signal proportional to the amplitude of the sinusoidal signal at frequency nF; means for providing a periodic signal, the frequency of which is a function of said sinusoidal signals at frequency F and nF; a second integrator for integrating said periodic signal for providing a second direct current signal; and means for providing said second signal in response to the provision of said first and second direct current signals.