Abstract: A technique for controlling print quality in an inkjet printer by delivering synchronized heating, non-printing pulses and printing pulses to the ink firing resistors during print firing operations such as during the printing of a swath. A temperature of the printhead substrate is measured and compared against a reference temperature during printing operations. If the measured temperature is below the reference temperature, then the printhead substrate is heated during the printing operations to bring the substrate up to the reference temperature. The heating is done by delivering synchronized heating non-printing pulses and printing pulses to the ink firing resistors during selected print firing periods, wherein either the heating pulses or the printing pulses, but not both, occur during a selected print firing period. The heating pulses are logically OR-ed with the printing pulses to achieve the synchronization.

Abstract: The volume of drops ejected from thermal ink jet printheads varies with the temperature of the printhead. The variation in drop volume degrades print quality by causing variations in the darkness in black and white text, the contrast of gray scale images, and variations in the chroma, hue, and lightness of color images. The present invention reduces the range of drop volume variation by reducing the range of printhead temperature variation during the print cycle by keeping the printhead temperature above a reference temperature. When the printhead temperature falls below the reference temperature during a print cycle the printhead is heated with nonprinting pulses.

Abstract: A Self Calibrating Color Printer. The present invention enables color printers to accurately reproduce color images despite variations in ink, paper or the printing system. The calibrated printer includes a movable optical sensor assembly which first calibrates itself by measuring an included known color gamut located within the movement range of the sensor assembly. Once calibrated, the sensor assembly measures a color print test pattern newly printed by a movable color print head of the printer. An analog-to-digital converter transforms electrical signals from the sensor assembly to sensor values in digital form, enabling a printer control processor to process the measured data, thereby producing two look-up tables stored in memory: first, a color correction look-up table which adjusts image color values to account for the ink/paper variations, and second, an error diffusion look-up table which spreads color value errors at a given pixel to its neighbors.

Abstract: Piezoelectric elements in a transducer array are individually excited and used to sense the back-scattered signal from fluid flowing within an interrogation volume. The array is preferably a 2-D phased array with a pitch no greater than one-half the acoustic wavelength of the interrogation signal. By activating the transducer elements as a pattern of concentric rings as viewed from a point of interrogation, and by suitable phasing and range-gating of an interrogation signal, a substantially spherical interrogation volume (SIV) is created. The return signal from the SIV provides an isotropic indication of the speed of flow of the fluid. The focussing distance along an interrogation axis can be changed by changing either the size of the aperture created by the pattern of activated elements or their relative phasing. The interrogation direction can be angled off-axis by activating the transducer elements in a pattern of concentric ellipses.

Abstract: An ink-cooled thermal ink jet printhead has an efficient heat exchanger located on the back side of the printhead that eliminates the need for heat sinks. All ink flowing to the firing chamber goes through the heat exchanger. The geometry of the heat exchanger is chosen so that almost all the residual heat absorbed by the printhead substrate is transferred to the ink as it flows to the firing chamber. Additionally, the pressure drop of the ink flowing through the heat exchanger is low enough so that it does not significantly reduce the refill rate of the firing chambers. The heat exchanger can have one or more active heat exchanger sides. The heat exchanger has little thermal mass itself and significantly reduces the thermal mass of printhead by eliminating the need for a heat sink. This reduces the warm-up time of the printhead to a fraction of a second.

Abstract: Pulses of ultrasound are focused in the patient's body to create an interrogation volume where a characteristic of blood flow is to be measured. The bandwidth of the back-scattered Doppler return signal is measured. In order to measure flow velocity independent of direction, the interrogation volume is generated substantially as a sphere in which the range dimension is set equal to the lateral dimensions (azimuth and elevation) of the interrogation signal. The Doppler bandwidth is then scaled to provide a direction-independent measurement of flow velocity. In order to determine the direction of flow, the interrogation volume is generated substantially as an ellipsoid. The long axis of the ellipsoidal interrogation volume is then rotated until the measured Doppler bandwidth is at a minimum, which is reached when the long axis is aligned with the flow direction.

Abstract: Pulses of ultrasound are focused in the patient's body to create an interrogation volume where either the magnitude of velocity or the direction of blood flow is to be measured. The strength of the back-scattered signal is measured for each pulse and the mean squared rate of change of the envelope of the range-gated signal is estimated. In order to measure flow velocity independent of direction, the interrogation volume is generated substantially as a sphere by creating an ultrasonic wave envelope in which the components of the mean square spatial gradient are equal in all directions. The estimated mean square rate of change of the envelope of the back-scattered signal is then scaled to provide a direction-independent measurement of flow velocity. In order to determine the direction of flow, the interrogation volume is generated substantially as an ellipsoid.

Abstract: An ultrasound probe includes an ultrasound emitter and a turbine. In one embodiment, the ultrasound emitter is a reflective surface which reflects ultrasound signals generated by a transmitter. The reflective surface reflects the ultrasound signals so that reflected ultrasound signals exit the ultrasound probe. The turbine is connected to the reflecting means. Fluid flowing through the turbine causes the turbine to rotate the reflecting means so that the reflected ultrasound signals sweep an area surrounding the ultrasound probe.

Abstract: This disclosure presents methods for controlling the temperature of a thermal ink jet and thermal printhead so that the quality of black and white printing, gray-scale printing, and color printing is improved. The methods control the average residual power of the columns of resistors so that the average residual power of an addressed column has a prescribed relationship to the average residual power of an unaddressed column. This is achieved by altering the magnitude of the drive voltages that drive the unaddressed resistors of the printhead matrix or by using nonprinting pulses. Methods for measuring the efficiency of the printhead are also presented.

Abstract: This document discloses a method and apparatus for real-time control of the temperature of thermal ink jet printheads and thermal printheads through the use of nonprinting pulses. A closed-loop system produces nonprinting pulses in response to a difference between a reference temperature signal and a printhead temperature signal produced by a temperature sensor on the printhead so that the printhead operates at a constant elevated temperature. The reference temperature signal can specify an operating temperature anywhere between 10.degree. C. and 100.degree. C. above room temperature. The closed-loop system can have multiple loops with different response times so that complex nonlinear responses to changes in the printhead temperature can be obtained. The open-loop system transmits nonprinting pulses to the printhead for each printing interval that the printer does not eject a drop. Also, this document discloses a method for measuring the energy transfer characteristics of a printhead.

Abstract: This disclosure presents methods for controlling the temperature of a thermal ink jet and thermal printhead so that the quality of black and white printing, gray-scale printing, and color printing is improved. The methods control the average residual power of the columns of resistors so that the average residual power of an addressed column has a prescribed relationship to the average residual powder of an unaddressed column. This is achieved by altering the magnitude of the drive voltage that drive the unaddressed resistors of the printhead matrix or by using nonprinting pulses. Methods for measuring the efficiency of the printhead are also presented.

Abstract: Several embodiments of an apparatus for directly driving all addressed and unaddressed resistive heating elements in a matrix of heating elements is disclosed. Since the unaddressed heating elements are directly driven, the parasitic voltages that are found across unaddressed heating elements in prior-art arrays are replaced with specified constant voltages. Additionally, the variation in total power dissipation of all the heating elements in the matrix can be reduced. When a matrix of directly driven heating elements is used in a thermal printer or thermal-ink-jet printer several advantages are realized. The directly driven unaddressed heating elements have a specified low voltage across them instead of a parasitic voltage which may have a magnitude large enough to cause the printhead to misfire. Additionally, the reduction in the variation of the total power dissipation reduces the variation in the printhead temperature which reduces the variation in the printed dot size.