Electro-optical material-based grey scale generating method

• US 6,795,064 B2
• Filed: 09/07/2001
• Issued: 09/21/2004
• Est. Priority Date: 04/30/1998
• Status: Expired due to Term

• Current Assignee: Wistron Corporation
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Walker, Richard C., Blalock, Travis N., Gaddis, Neela B.
• Primary Examiner(s): Shankar, Vijay
• Application Number:
  US09/948,732
• Publication Number:
  US 20020021267A1
• Time in Patent Office: 1,110 Days
• Field of Search: 345/81, 345/82, 345/87, 345/89, 345/90, 345/92, 345/96, 345/98, 345/100, 345/102, 345/204, 345/690
• US Class Current: 345/204
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0259 with use of an analog or digital ramp generator in the column driver or in the pixel circuit
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only

Abstract

A grey scale is generated by modulating light in response to an information signal using an electro-optical material. An analog sample is derived from the information signal, a drive signal is generated in response to the analog sample and the drive signal is applied to the electro-optical material. The drive signal has a sequence of a first temporal portion and a second temporal portion. The first temporal portion has a temporal duration that has a pre-determined relationship to the analog sample, and the second temporal portion is the temporal complement of the first temporal portion.

Claims

1. A method of generating a grey scale in response to an information signal, the grey scale being generated by modulating light using an electro-optical material, the method comprising:

deriving an analog sample from the information signal;

in response to the analog sample, generating a drive signal including a sequence of a first temporal portion and a second temporal portion, the first temporal portion having a temporal duration that has a pre-determined relationship to the analog sample, the second temporal portion being a temporal complement of the first temporal portion; and

applying the drive signal to the electro-optical material.

2. The method of claim 1, in which:

in generating the drive signal;

the sequence of the first temporal portion and the second temporal portion is a first sequence of the first temporal portion and the second temporal portion, and

the drive signal is generated in a first electrical sense during the first temporal portion and is generated in an opposite electrical sense during the second temporal portion in the first sequence; and

the method additionally comprises generating the drive signal to additionally include a second sequence of the first temporal portion, in which the drive signal is generated in the opposite electrical sense, and the second temporal portion, in which the drive signal is generated in the first electrical sense, the first temporal portion and the second temporal portion being in any temporal order in the second sequence.

3. The method of claim 2, additionally comprising illuminating the electro-optical material in synchronism with the drive signal.

4. The method of claim 3, in which, illuminating the electro-optical material includes illuminating the electro-optical material during the first sequence of the drive signal.

5. The method of claim 1, in which:

generating the drive signal is subject to an error factor that changes the predetermined relationship between the duration of the first temporal state and the analog sample; and

the method additionally comprises minimizing a visual effect of the error factor on the gray scale.

6. The method of claim 5, in which:

the error factor has a sense;

the information signal includes odd-numbered sequences interleaved with even-numbered sequences;

deriving the analog sample, generating the drive signal and applying the drive signal are performed in response to each of the sequences; and

minimizing the visual effect of the error factor on the gray scale includes inverting the sense of the error factor when generating the drive signal in response to one of (a) the odd-numbered sequences and (b) the even-numbered sequences.