Liquid crystal eyeglass

• US 4,919,520 A
• Filed: 11/18/1988
• Issued: 04/24/1990
• Est. Priority Date: 08/31/1984
• Status: Expired due to Fees

• Current Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Original Assignee: Olympus Optical Corporation Limited (Olympus Corporation)
• Inventors: Okada, Takao, Nakamura, Kazuo, Yamamoto, Hiroyuki, Nakamura, Takeaki, Nishioka, Kimihiko, Tomabechi, Hideo, Kouchi, Toshihito
• Primary Examiner(s): Miller, Stanley D.
• Assistant Examiner(s): Phan, Trong Quang
• Application Number:
  US07/273,238
• Time in Patent Office: 522 Days
• Field of Search: 350/331 R, 350/331 T, 350/347 R, 350/347 V, 350/335, 351/41, 351/49, 351/58, 351/168
• US Class Current: 349/13
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G02C 7/08 Auxiliary lenses; Arrangements for varying focal length
• CPC Class Codes: G02C 7/083 Electrooptic lenses
• CPC Class Codes: G02C 7/101 having an electro-optical light valve electro-optical elements per se G02F
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/29 for the control of the position or the direction of light beams, i.e. deflection
• CPC Class Codes: G02F 1/294 Variable focal length devices

Abstract

Liquid crystal eyeglasses include a detector for detecting a physical quantity which varies with the temperature of the liquid crystal, the orientation of molecules of the liquid crystal or a change in the refractive index of the liquid crystal. The voltage applied to the liquid crystal is controlled in accordance with an output signal from the detector, thus compensating for a change in the refractive index of the liquid crystal which is attributable to a temperature change and maintaining the refractive index constant.

Claims

1. A liquid crystal eyeglass comprising:

an eyeglass frame having a frame portion for at least partially surrounding a lens;

at least one lens assembly supported within said frame portion having a predetermined effective aperture and including a liquid crystal having a refractive index which varies as a result of a change in the orientation of molecules of a liquid crystal responsive to the application of an external voltage;

means for detecting the temperature of the liquid crystal comprising a temperature sensor disposed upon the portion of the frame surrounding said lens assembly and outside of said predetermined effective aperture, said detecting means further including temperature detecting and processing means for generating a compensating signal;

comparison means for generating a differential signal representing a deviation of said compensating signal from a known signal value; and

voltage control means for controlling the voltage applied to the liquid crystal responsive to a control output from the comparison means, for controlling the orientation of the liquid crystal to compensate for a change in the refractive index of the liquid crystal due to a change in temperature.

2. A liquid crystal eyeglass according to claim 1 in which the temperature sensor comprises one of the temperature sensors of a group including a thermistor, a thermocouple, a temperature measuring resistor and a temperature measuring impedance.

3. A liquid crystal eyeglass according to claim 1 further including a solar cell mounted upon the surface of a portion of the frame surrounding said liquid crystal for charging a power supply used to power the detecting means and the voltage control means.

4. A liquid crystal eyeglass according to claim 1 in which said liquid crystal eyeglass comprises a pair of spaced transparent plates;

a common transparent plate positioned between said pair of spaced transparent plates dividing the region between said pair of plates substantially evenly into first and second interior regions;

and sealing means for liquid tightly sealing said interior regions, said interior regions each containing a liquid crystal;

the crystals having their optical axes orthogonal to each other and orthogonal to the optical axis of the lens to provide a variable focal length lens for providing a change in focal length independently of the direction of polarization of the incident light.

5. A liquid crystal eyeglass according to claim 4 wherein transparent electrodes are arranged on both surfaces of said common transparent plate and upon the interior surfaces of said pair of transparent plates;

and

means for coupling said voltage control means to selected ones of said transparent electrodes.

6. A liquid crystal eyeglass according to claim 5 in which said transparent plates are flat planar members.

7. A liquid crystal eyeglass according to claim 4 wherein said common transparent plate is provided with a sensing transparent electrode provided on one surface thereof and electrically insulated from the first mentioned transparent electrode on said one surface;

said detecting means being coupled to said sensing electrode for detecting a characteristic of the liquid crystal which changes as a function of temperature.

8. A liquid crystal eyeglass according to claim 7 further comprising means for periodically coupling said sensing electrode to said temperature detecting means.

9. A liquid crystal eyeglass according to claim 4 in which the interior surfaces of said pair of transparent plates each have a Fresnel structure, said electrodes being deposited upon said Fresnel structure.

10. A liquid crystal eyeglass according to claim 1 in which the voltage control means is formed by a voltage control circuit including a temperature change response correction circuit and a variable voltage output circuit.

11. A liquid crystal eyeglass according to claim 1 in which the voltage control means includes a plurality of control inputs each associated with a focal length and signal switching means for selectively coupling a reference level to one of said control inputs which permits one of a plurality of said focal lengths to be established for the liquid crystal eyeglass.

12. A liquid crystal eyeglass employing a liquid crystal having a refractive index which varies as a result of a change in the orientation of molecules of the liquid crystal in response to the application of an external voltage, comprising:

means for detecting the temperature of the liquid crystal;

voltage control means for controlling the voltage applied to the liquid crystal in response to a detection output from the temperature detecting means, thereby controlling the orientation of the liquid crystal to compensate for a change in the refractive index of the liquid crystal due to a temperature change;

said voltage control means being formed by a voltage control circuit including a temperature change response correction circuit and a variable voltage output circuit;

said variable output circuit controlling the amplitude of an AC output voltage supplied from a power supply in accordance with the level of a control voltage which is applied to a control terminal thereof.

13. A liquid crystal eyeglass employing a liquid crystal having a refractive index which varies as result of a change in the orientation of molecules of the liquid crystal in response to the application of an external voltage comprising:

means for detecting one of the characteristics of the liquid crystal including the temperature and the orientation of the liquid crystal; and

means for controlling the frequency of the voltage applied to the liquid crystal in response to a detection output from the detecting means, whereby the orientation of the liquid crystal is controlled to compensate for a change in the refractive index of the liquid crystal due to a temperature change.

14. A liquid crystal eyeglass according to claim 13 in which the temperature detecting means comprises a temperature sensor taken from the group including a thermistor, a thermocouple, a temperature measuring resistor, a temperature measuring impedance and a temperature detecting and processing unit.

15. A liquid crystal eyeglass according to claim 13 in which the orientation detecting means comprises means for detecting a capacitance representing a physical quantity which varies with a change in the orientation of molecules of the liquid crystal.

16. A liquid crystal eyeglass according to claim 13 in which the frequency control means is formed by a frequency control circuit including a temperature change response correction circuit, and a variable frequency output circuit which delivers oscillation waves of a frequency which depends on the level of a voltage applied to an input terminal thereof.

17. A liquid crystal eyeglass according to claim 16 in which an input to the frequency control circuit is supplied from a control means comprising an analog switch, a multivibrator for delivering output pulse waves having an oscillation frequency which depends on the values of a resistor connected to a resistance terminal thereof and a capacitance connected to a capacitance terminal thereof, the analog switch being operated by an output pulse from a pulse generator to connect a non-grounded electrode of the liquid crystal lens to the capacitance terminal of the multivibrator, said control means also comprising a frequency-to-voltage converter for converting the frequency of the output pulse waves from the multivibrator into a corresponding voltage, a sample-and-hold circuit for sampling and holding an output voltage from the converter, and a comparator for comparing an output voltage from the sample-and-hold circuit against a reference voltage.

18. A liquid crystal eyeglass according to claim 13 in which the frequency control means includes a plurality of control inputs each associated with a focal length and signal switching means for selectively coupling a reference level to one of said control inputs to control the output frequency of said frequency control means which permits one of a plurality of said different focal lengths to be established for the liquid crystal eyeglass.

19. The liquid crystal eyeglass of claim 13 wherein said detecting means comprises a multivibrator coupled to said liquid crystal for generating an output signal whose frequency varies with changes in the impedance of the liquid crystal due to changes in temperature.

20. The liquid crystal eyeglass of claim 19 wherein said converter means is a frequency-to-voltage converter.

21. A liquid crystal eyeglass employing a liquid crystal arranged in an eyeglass frame and having a varying refractive index as a result of a change in the orientation of molecules of the liquid crystal in response to the application of an external voltage, comprising:

means for detecting a physical quantity which varies with a change in the orientation of molecules of the liquid crystal;

voltage control means for controlling the voltage applied to the liquid crystal in response to a detection output from the detecting means, thereby compensating for a change in the refractive index of the liquid crystal which occurs responsive to a change in temperature;

said means for detecting a physical quantity comprising one of the means taken from the group consisting of means for detecting a current flow through the liquid crystal and means for detecting a capacitance which varies with a change in the orientation of molecules of the liquid crystal; and

said voltage control means being formed by an applied voltage control circuit including a temperature change response correction circuit, and a variable voltage output circuit for controlling the amplitude of an AC voltage supplied from a DC/AC converter in accordance with the level of the control voltage applied to said variable voltage output circuit.

22. A liquid crystal eyeglass according to claim 21 in which an input to the applied voltage control circuit is fed from a control means comprising an analog switch, a multivibrator for delivering output pulse waves of an oscillation frequency which is determined by the value of a resistance and a capacitance connected to a resistance terminal and a capacitance terminal thereof, the analog switch being operated by an output pulse from a pulse generator to connect a non-grounded electrode of the liquid crystal lens to the capacitance terminal of the multivibrator, said control means also comprising a frequency-to-voltage converter for converting the frequency of the output pulse waves from the multivibrator into a corresponding voltage, a comparator for comparing an output voltage from the converter against a reference voltage, and a sample-and-hold circuit for sampling and holding an output voltage from the comparator.

23. A liquid crystal eyeglass including:

a frame;

a liquid crystal mounted on said frame and having control electrodes and exhibiting a varying refractive index as a result of a change in the orientation of molecules of the liquid crystal in response to the application of an external voltage from a source mounted on said frame and coupled to said control electrodes;

means for detecting a physical quantity which varies with a change in the orientation of molecules of the liquid crystal;

voltage control means for controlling the voltage applied to the liquid crystal in response to a detection output from the detecting means, thereby compensating for a change in the refractive index of the liquid crystal which occurs in response to a temperature change;

pulse generator means;

analog switch means for alternately coupling said detecting means and said voltage control means to said liquid crystal at a repetition rate determined by said pulse generator means, whereby said liquid crystal is alternately powered and monitored in a continuing, repetitive manner; and

said applied voltage control means includes a plurality of control inputs each associated with a focal length and signal switching means for selectively coupling a reference level to one of said control inputs which permits one of a plurality of said different focal lengths to be established for the liquid crystal eyeglass.