Patents by Inventor Wilbert J. A. M. Hartmann

Wilbert J. A. M. Hartmann has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Ferroelectric display device with temperature compensation
    Patent number: 5805131
    Abstract: To compensate for the variation of the transmission-voltage characteristic curve due to temperature changes in a ferro-electric display device, the display device is provided with one or more measuring elements (5) for measuring the polarization current. The drive voltages are corrected by means of the polarization current which is used as a feedback parameter.
    Type: Grant
    Filed: October 2, 1996
    Date of Patent: September 8, 1998
    Assignee: U.S. Philips Corporation
    Inventors: Wilbert J. A. M. Hartmann, Franciscus H. A. Lathouwers
  • Display device with crossing electrodes with specific ratio for gray scale
    Patent number: 5404236
    Abstract: An electro-optic display device with grey scale set by areas of crossing electrodes. In one embodiment, there are 3 strip-shaped sub electrodes with a width relationship of 4:2:1, and two strip shaped column electrodes with a relationship of 8:1. In a second embodiment, there are 4 strip-shaped sub electrodes with a width relationship of 8:4:2:1, and two strip shaped column electrodes with a relationship of 16:1.
    Type: Grant
    Filed: July 8, 1994
    Date of Patent: April 4, 1995
    Assignee: U.S. Philips Corporation
    Inventors: Wilbert J. A. M. Hartmann, Johannes A. M. M. Van Haaren, Antonius G. H. Verhulst
  • Electro-optic display device with increased number of transmission levels
    Patent number: 5208689
    Abstract: An LCD device in which the pixels are divided into sub-pixels composed of one analog adjustable sub-pixel and a plurality of digitally controlled other sub-pixels. By combining a discrete adjustment of the (sub)-transmission levels of the other sub-pixels with an analog adjustment of transmission levels of the one sub-pixel, the total number of light transmission levels is increased considerably. The analog adjustment thus is less critical because the greater part of the ultimate level is defined by the accurate discrete adjustment.
    Type: Grant
    Filed: August 19, 1991
    Date of Patent: May 4, 1993
    Assignee: U.S. Philips Corporation
    Inventors: Wilbert J. A. M. Hartmann, Leonard J. M. Esser, Antonius G. H. Verhulst, Johannes A. M. M. Van Haaren
  • Ferroelectric liquid crystal display having a spread of angles for grayscale and method of manufacture
    Patent number: 5151804
    Abstract: A liquid crystal device incorporating ferroelectric liquid crystal medium having smectic layers between two supporting plates provided with electrodes, the smectic layers exhibiting a spread of angles with respect to at least one of the supporting plates, whereby a gradual transmission/voltage characteristic is achieved. The spread of angles can be obtained by any of several techniques, such as subjecting the device to a low frequency electric field, or a local thermal, mechanical, chemical or magnetic treatment.
    Type: Grant
    Filed: June 11, 1990
    Date of Patent: September 29, 1992
    Assignee: U.S. Philips Corporation
    Inventors: Antonius G. H. Verhulst, Wilbert J. A. M. Hartmann, Franciscus J. Stommels, Ann M. M. Luyckx-Smolders
  • Method of driving a passive ferro-electric liquid crystal display device
    Patent number: 5047758
    Abstract: In a method of driving a passive ferro-electric display device the selection voltages, "blanking" voltages and data voltages are given a bipolar character so that the values of the data voltages with respect to the "blanking" voltage can be chosen to be so low that there is substantially no crosstalk. In a passive display device this provides the possibility of driving large numbers of lines (for example, for LCD-TV) while maintaining the contrast.
    Type: Grant
    Filed: November 9, 1990
    Date of Patent: September 10, 1991
    Assignee: U.S. Philips Corporation
    Inventors: Wilbert J. A. M. Hartmann, Karel E. Kuijk
  • Method of driving a ferroelectric to display device to achieve gray scales
    Patent number: 4976515
    Abstract: In the case of active drive of a ferro-electric liquid crystal display device the picture elements within the line selection period are first brought to an extreme state by means of a "blanking" signal. To obtain grey scales in a reproducible manner (via charge compensation) the data signal is preferably presented during a period which is short with respect to the switching period of the ferro-electric liquid crystal.
    Type: Grant
    Filed: December 12, 1988
    Date of Patent: December 11, 1990
    Assignee: U.S. Philips Corporation
    Inventor: Wilbert J. A. M. Hartmann
  • Method of driving a ferroelectric liquid crystal display device and associated display device to achieve gray scale
    Patent number: 4840462
    Abstract: By using an auxiliary signal bringing a ferroelectric liquid crystal to an extreme transmission state in an active matrix it is impossible for successive charge compensation to occur on the pixels. This prevents the growth of regions where transmission occurs or does not occur and provides the possibility of obtaining gray scales in a reproducible manner.
    Type: Grant
    Filed: February 25, 1988
    Date of Patent: June 20, 1989
    Assignee: U.S. Philips Corporation
    Inventor: Wilbert J. A. M. Hartmann