System for making a thermo-active device temperature dependent

• US 4,621,261 A
• Filed: 12/19/1983
• Issued: 11/04/1986
• Est. Priority Date: 12/21/1982
• Status: Expired due to Fees

• Current Assignee: Thomson-CSF (Thales SA)
• Original Assignee: Thomson-CSF (Thales SA)
• Inventors: Hehlen, Robert, Marcenac, Philippe
• Primary Examiner(s): Yusko, Donald J.
• Application Number:
  US06/563,244
• Time in Patent Office: 1,051 Days
• Field of Search: 340/825.52, 340/825.81, 340/785, 340/811, 340/813, 340/825.86, 350/331 T, 350/350.5
• US Class Current: 345/101
• CPC Class Codes: G02F 1/133382 Heating or cooling of liquid crystal cells other than for activation, e.g. circuits or arrangements for temperature control, stabilisation or uniform distribution over the cell
• CPC Class Codes: G09G 3/3603 with thermally addressed liquid crystals

Abstract

A system for making a device temperature dependent whose operation is dependent on the local heating applied to a thermo-active material layer. The invention uses the heating electrodes of the device as temperature sensors, the information detected by these sensors being stored in a memory and used as bases for establishing the temperature dependence.

Claims

1. A temperature-dependent addressing system comprising:

a temperature-dependent device whose operation depends on the local heating applied to a layer of thermo-active material;

means for producing said local heating, including an assembly of electrodes and a means for passing a transitory electric current through one of said electrodes wherein said assembly of electrodes are situated in the immediate vicinity of said layer;

a memory means containing data pertaining to the thermal control of said electrodes;

a means for thermally addressing said one electrode as a function of said data wherein each one of said assembly of electrodes comprises a conducting material having a temperature coefficient;

a resistance r connected to the output of said electrode wherein at least a portion of said heating current passes through said resistance r, and whereby the potential difference v appearing at the terminals of said resistance r is proportional to the heating of said one electrode;

an analogue-digital converter which transmits for each of said heating electrodes, said potential difference v to one of the inputs of a comparator wherein the second input of said comparator receives said data relative to the thermal control of said electrode;

circuit means for adjusting the heating time of said electrode wherein said circuit means is connected to the output of said comparator.

2. The system as claimed in claim 1, wherein said heating electrode (R_j) forms part of an assembly of electrodes through which said heating current (i) passes periodically and which have a common electric point, said electric resistance r being also electrically connected to this point.

3. The system as claimed in claim 1, wherein said layer is disposed between two crossed electrode networks, one of said networks being formed by said heating electrodes.

4. The system as claimed in claim 1, wherein said material is an electro-optical material.

5. The system as claimed in claim 4, wherein said electro-optical material is a liquid crystal having a smectic phase.

6. The system as claimed in claim 5, wherein said smectic liquid crystal is a mixture of several substances.

7. The system as claimed in claim 1, wherein said material has magneto-optical properties.

8. The system as claimed in claim 1, wherein said memory is a programmable memory used for read-out.

9. The system as claimed in claim 1, wherein said memory is a random access memory, said system comprising a write-in step which may be renewed.

10. The system as claimed in claim 1, wherein said memory is a random access memory and wherein said potential difference v for each of said electrodes of said assembly are written into said memory whereby said memory contains information relative to said potential difference v present at said terminals of said resistance r for each heating electrode after said time;

means for making said device temperature-dependent as a result of said data stored in said memory wherein said means includes a potentiometer for allowing for the overall temperature adjustment of said device.