Spatial light modulators

• US 5,339,090 A
• Filed: 09/10/1992
• Issued: 08/16/1994
• Est. Priority Date: 06/23/1989
• Status: Expired due to Term

• Current Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Original Assignee: Northern Telecom Limited (Nortel Networks Corporation)
• Inventors: Collings, Neil, Vass, David, Crossland, William A.
• Primary Examiner(s): Oberley, Alvin E.
• Assistant Examiner(s): Liang, Regina
• Application Number:
  US07/943,134
• Time in Patent Office: 705 Days
• Field of Search: 340/718, 340/719, 340/784, 340/803, 340/805, 340/825.81, 340/825.82, 340/825.86, 340/825.87, 340/763, 340/765, 359/55-57, 359/72, 362/23, 345/204, 345/205, 345/206, 345/90-92, 345/50, 345/51, 345/48
• US Class Current: 345/90
• CPC Class Codes: G02F 1/1354 having a particular photoconducting structure or material
• CPC Class Codes: G02F 1/136 Liquid crystal cells structurally associated with a semi-conducting layer or substrate, e.g. cells forming part of an integrated circuit G02F1/135 takes precedence
• CPC Class Codes: G06E 1/02 operating upon the order or content of the data handled
• CPC Class Codes: G06N 3/0675 using electro-optical, acousto-optical or opto-electronic means
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0828 forming a digital to analog [D/A] conversion circuit
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor

Abstract

A smart pixel is comprised by a chiral smectic liquid crystal light modulator (45) (ferro-electric or electroclinic) disposed on a semiconductor substrate and having associated therewith electronic circuitry (41-44) formed in the semiconductor substrate in particular a single crystal silicon VLSI substrate, which circuitry is such as to provide localised intelligence (electrical signal processing and conditioning, pointwise operations, logic functions) at the modulator. The circuitry may comprise photodetector/threshold circuitry (FIG. 7) or digital-to-analogue conversion (FIGS. 3 or 4), for example.

Claims

1. A smart spatial modulator device whose output comprises an optical beam modulated in accordance with optical and/or electronic input signals, the device including a pixel comprising:

a chiral smectic liquid crystal material disposed between a semiconductor substrate carrying a first electrode and a panel carrying a second electrode;

first electronic circuitry formed in the semiconductor substrate in the vicinity of the first electrode for changing the sate of the liquid crystal material;

further electronic circuitry formed in the semiconductor substrate in the vicinity of the first electrode to provide pointwise operations at the pixel, said pointwise operations including logic function, amplification and thresholding;

a photodetector outputs said optical input signal for addressing said pixel;

said further electronic circuitry includes an electronic input circuitry which outputs said electronic input signal for addressing said pixel in addition to the addressing by said optical input signal or alternatively to the addressing by said optical input signal, said first and further electronic circuitry acting instantaneously to process said input optical and/or electronic signal or signals and to change the state of the liquid crystal material to modulate the output optical beam and/or to provide an electronic output in accordance with the processing carried out;

the device further including a plurality of said pixels, said plurality of pixels being in combination with neighboring pixels to form an array, and each pixel of the plurality individually performs an identical logic function to the other pixels of the plurality, the array performs one of a plurality of different respective logic functions in dependence on the interconnection of said plurality of pixels.

2. A smart spatial light modulator device as claimed in claim 1 and including a plurality of pixels, said pixel comprising one of the plurality of pixels and being in combination with neighbouring pixels of the plurality of pixels.

3. A smart spatial light modulator device as claimed in claim 1 wherein the semiconductor substrate is of silicon.

4. A smart spatial light modulator device as claimed in claim 3 wherein the first and further electronic circuitry is formed by VLSI technology.

5. A smart spatial light modulator device as claimed in claim 1 and wherein said logic functions are performed on an electrical signal comprising the output of the photodetector and corresponding to the optical input signal, which logic function is performed being determined by application of corresponding electrical control signals to the further electronic circuitry.

6. A smart spatial light modulator device as claimed in claim 1 and wherein said logic functions are performed on an electrical signal comprising the output of the photodetector and corresponding to the optical input signal, which logic function is performed being determined by control codes stored in memory registers of the further electronic circuitry.

7. A smart spatial light modulator device as claimed in claim 1 and wherein information is carried between the logic functions associated with different pixels in the array by optical signals.

8. A smart spatial light modulator device as claimed in claim 1 and wherein the chiral smectic liquid crystal material is a ferroelectric effect chiral smectic liquid crystal material.

9. A smart spatial light modulator device as claimed in claim 1 and wherein the chiral smectic liquid crystal material is an electroclinic effect chiral smectic liquid crystal material.