The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 11, 2003
Filed:
Oct. 28, 1999
Rene P. Helbing, Palo Alto, CA (US);
Akinobu Kuramoto, Pleasanton, CA (US);
Geraint Owen, Palo Alto, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A ferroelectric liquid crystal-based light valve system with contrast control and a method for controlling contrast in a ferroelectric liquid crystal-based light valve system. The light valve system includes a light input, a ferroelectric liquid crystal-based spatial light modulator, an analyzer, and a voltage controller. The ferroelectric liquid crystal-based spatial light modulator includes signal processing electronics and an array of pixels. The array of pixels is configured to receive light from the light input and includes an array of pixel electrodes, a transparent electrode, and a layer of ferroelectric liquid crystal material. Each pixel electrode is independently switchable between a first voltage level and a second voltage level by the signal processing electronics. One of these levels may be a variable input voltage level. The analyzer has orthogonal directions of maximum transmissivity and minimum transmissivity. The voltage controller is configured to adjust at least one of the first voltage level and the second voltage level through a first range of voltages and a second range of voltages, respectively. As the voltage controller adjust the variable input voltage level, the direction of polarization of light exiting the pixels may rotate by at least 2 degrees in order to precisely align the direction of polarization with the direction of minimum transmissivity. The light valve system may further comprise a light intensity sensor and a feedback circuit in electrical communication with the light intensity sensor and the voltage controller. The method of controlling contrast in a ferroelectric light valve system begins by providing a ferroelectric liquid crystal-based spatial light modulator that includes a plurality of pixels and signal processing electronics. The signal processing electronics independently switch an electric field across each of the plurality of pixels between a forward direction and a reverse direction. An analyzer having a direction of minimum transmissivity is also provided. The pixels are then illuminated and a contrast control signal is detected. Detecting the control signal may include checking for an input from a contrast control user interface. Detecting the control signal may also include providing an automatic contrast control feedback circuit. The second direction of polarization is then rotated by changing the magnitude of the electric field across the plurality of pixels in response to the control signal.