JPS63221326A - Liquid crystal element driving device - Google Patents

Abstract

PURPOSE:To permit compensation of the nonlinearity of input and output characteristics with simple constitution by detecting the liquid crystal molecular orientation state of a liquid crystal element for monitor and feeding back the detection signal thereof to form a driving signal. CONSTITUTION:A light beam is projected from a light source 3 to the liquid crystal element 2 for monitor having nearly the same optical characteristics at the optical output characteristics of the liquid crystal element to be subjected to driving control and the transmitted light thereof is detected by a photodetector 4. The output of the detector 4 is supplied to a feedback amplifier 5. A distance signal from the element 1 to an object is supplied to the other input terminal of the amplifier 5. The amplifier 5 detects the differential component of both signals and supplies the output signal thereof to amplitude modulators 6 and 8. The output signals thereof have the characteristic to constitute an inverse function to the molecular arrangement of the element 2. The modulators 6 and 8 respectively modulate the output signals of the amplifier 5 and supply the same as driving signals to the element 2 and the element 1. The element 1 is thereby driven in the optical output characteristic of the function linear to the input signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a voltage-controlled liquid crystal element driving device, and particularly to a liquid crystal element driving device that can obtain linear optical output characteristics with respect to an input signal. be.

(Prior Art) Voltage-controlled liquid crystal elements are capable of changing the alignment state of liquid crystal molecules by an external driving voltage and changing their effective transmittance and refractive index, and have been put into practical use as various optical elements. For example, a liquid crystal lens that can variably control the alignment state of liquid crystal molecules in the cell by applying an external voltage and changing its effective value, and by changing its effective refractive index, the focal length can be continuously changed. Light control filters that can vary the intensity of transmitted light have been devised. Furthermore, the present inventor has proposed an autofocus lens that can automatically adjust the focal length by combining a liquid crystal element and a distance sensor in Japanese Patent Application Laid-Open No. 60-1985114.

When driving these liquid crystal elements, an external input signal is used as a drive signal, and this drive signal changes the optical output characteristics such as transmittance and refractive index. Therefore, the optical output characteristics are linear with respect to the input signal. It is desirable to achieve
For example, when using a liquid crystal element as an autofocus lens, it is desirable that the focal length changes linearly with respect to the output signal from the distance sensor.

However, since the focal length of the liquid crystal lens with respect to the driving signal voltage changes nonlinearly as shown in FIG. 4, it is necessary to compensate for this nonlinear characteristic using the driving device. Such nonlinear characteristics occur in almost the same way when twisted nematic liquid crystal (TN liquid crystal) and guest-host liquid crystal (G) (liquid crystal) are used as the liquid crystal element. Therefore, it is necessary to similarly compensate for nonlinear characteristics in dimming filters and display elements using TN liquid crystals or GH liquid crystals.

(Problem to be Solved by the Invention) In order to compensate for the nonlinear characteristics of the liquid crystal element described above, it is possible to use a folded line approximation method in which the characteristic curve is approximated by many straight lines, or to compensate for the nonlinear characteristics of the liquid crystal element. A method of generating a special function of the shape can be considered, but this requires the use of expensive and complicated electronic devices, microcomputers, etc., which complicates the structure of the drive device and increases manufacturing costs. There were drawbacks.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a liquid crystal element driving device capable of eliminating the above-mentioned drawbacks and compensating for nonlinear characteristics between an input signal and an optical output characteristic with a simple configuration.

(Means for Solving the Problems) A liquid crystal element driving device according to the present invention includes a liquid crystal element for a monitor having almost the same optical output characteristics as the optical output characteristic of the liquid crystal element to be driven and controlled, and a device for detecting the orientation state of liquid crystal molecules in a liquid crystal element; and a device for detecting the liquid crystal element for monitoring based on a detection signal from the detection device and an input signal instructing a desired optical output state of the liquid crystal element to be measured. The present invention is characterized in that it includes a feedback amplifier that generates an output signal to be driven, and is configured to drive a liquid crystal element to be driven and controlled based on the output signal from the feedback amplifier.

(Function) In order to compensate for the nonlinear characteristics of a liquid crystal element, changes in liquid crystal molecular alignment due to external voltage application are detected as changes in optical transmission characteristics or changes in electrical characteristics, and a voltage is created that is an inverse function of the characteristics. When used as a drive signal for driving a liquid crystal element, it acts to cancel out the nonlinear characteristics of the liquid crystal element by T degrees, so that the nonlinear characteristics of the liquid crystal element can be compensated for.

That is, for example, by combining a distance sensor that generates a voltage proportional to the relative distance between a liquid crystal lens and an object and a driving device according to the present invention, an autofocus lens with excellent characteristics can be constructed.

Furthermore, by combining the driving device according to the present invention with a DINHa element, a GH liquid crystal element, and an optical sensor that generates a voltage proportional to the light intensity (brightness), the transmitted light intensity changes in proportion to the external brightness. It can be used as a dimmer filter, and by using a variable voltage source instead of the optical sensor, it can also be used as a dimmer filter that can linearly and continuously vary the transmitted light intensity. Furthermore, since the display characteristics of the intermediate I (gray scale) in the liquid crystal display element are linear, it can also be applied to a liquid crystal display element having excellent display characteristics of the intermediate 111i;1.

(Embodiment) FIG. 1 is a diagram showing the configuration of an example of a liquid crystal element driving device according to the present invention. In this example, an example of driving and controlling a liquid crystal element for an autofocus lens will be described. Kaku11J 11'II
A liquid crystal element 1 for an autofocus lens to be used is used.

This liquid crystal element is composed of a liquid crystal whose refractive index changes as the alignment state of liquid crystal molecules changes depending on the driving voltage, and for example, a nematic liquid crystal with positive dielectric anisotropy can be used. As described above, since the liquid crystal element 1 has a nonlinear characteristic in which the change in focal length with respect to the driving voltage is nonlinear, a liquid crystal element 2 for a monitor having almost the same optical output characteristic as this nonlinear optical output characteristic is used. In this example, a guest liquid crystal element 2 whose transmittance changes according to the driving voltage is used as the liquid crystal element 2 for this monitor.
Uses host liquid crystal. This GH liquid crystal has a homogeneous arrangement characteristic in which a dichroic dye (guest) is dissolved in a nematic liquid crystal (host) with positive dielectric anisotropy. In this monitor liquid crystal element 2, the cell thickness and dye concentration are adjusted so that the change in transmittance with respect to the driving voltage as shown in FIG. 2 is almost the same as the characteristics of the liquid crystal element 1 shown in FIG. 4. Light from, for example, a semiconductor laser is directed toward this monitor liquid crystal element 2! ! A light beam is projected from 13, and the transmitted light is received by a photodetector 4. Since the light beam from the light source 3 is absorbed depending on the alignment state of the liquid crystal molecules in the monitor liquid crystal element 2, the output signal from the photodetector 4 indicates the alignment state of the liquid crystal molecules in the monitor liquid crystal element 2. become. The output signal of the photodetector 4 is amplified and converted into voltage, and then supplied to one input terminal of the feedback amplifier 5. The other input terminal of the feedback amplifier 5 has a liquid crystal element 1 measured by a distance sensor (not shown).
provides an input signal representing the distance from the object to the object. The input signal from this distance sensor has a voltage output proportional to the distance from the liquid crystal element to the object, and becomes a signal that supports the distance to the imaging point of the liquid crystal element 1 to be driven. Feedback amplifier 5 detects a difference component between the output signal of photodetector 4 and the input signal, and supplies this output signal to amplitude modulator 6 .

This output signal has a characteristic that is an inverse function to the molecular arrangement of the monitor liquid crystal element. In the amplitude modulator 6, the oscillator 7
The output signal from the feedback amplifier 5 is amplitude-modulated based on the IKHz square wave signal supplied from the feedback amplifier 5, and this modulated signal is supplied to the monitor liquid crystal element 2 as a drive signal. With this configuration, a feedback loop is formed to bring the monitor liquid crystal element 2 into a desired alignment state, and the monitor liquid crystal element 2 can be instantly brought into the desired alignment state.

On the other hand, the output signal from the feedback amplifier 5 is sent to another amplitude amplifier 7.
supply to. Amplitude modulation is performed in the amplitude amplifier 8 based on the square wave signal of the IKH 7 from the oscillator 7, and this modulation signal is amplified to an appropriate gain in the amplifier 9 and supplied as a drive signal to the liquid crystal element 1 to be controlled. With this configuration, the liquid crystal element 1 is driven and controlled by a drive signal that is an inverse function to the molecular orientation of the liquid crystal itself, and therefore, as shown in FIG. The drive will be controlled by the optical output characteristics of. By driving and controlling the liquid crystal element in this manner, it can function as an all-electronic automatic focusing lens without mechanically moving parts.

The present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the above embodiment, an example was explained in which the liquid crystal element for an autofocus lens was drive-controlled, but both the liquid crystal element to be driven and controlled and the monitor liquid crystal element were
By configuring it with N liquid crystal elements, it can also function as a dimming filter having transmission characteristics proportional to the input signal.

Furthermore, the present invention can also be applied to display elements that linearly display halftones depending on the input voltage.

Furthermore, in the above embodiment, a 1KH2 square wave was used to create a driving signal for the guest/host liquid crystal element for monitoring, but signals of other frequencies may be used as long as the frequency can operate the guest/host liquid crystal element. can be used, and furthermore, a sine wave, a distorted wave, etc. can also be used.

Furthermore, if the liquid crystal element can be driven with a DC voltage signal, an amplitude modulator is not necessary.

Furthermore, since the capacitance of a homogeneously aligned liquid crystal element changes in response to applied voltage in a manner similar to the characteristics shown in Figure 2, when electrically detecting changes in the alignment of liquid crystal molecules, , detected as a change in capacitance of the liquid crystal element,
A reverse voltage can be similarly obtained by incorporating this into a part of the oscillation circuit, by using conventional techniques such as AD-DA conversion, and by combining it with the negative feedback amplifier shown in FIG.

(Effects of the Invention) As described above, according to the present invention, a liquid crystal element for a monitor having almost the same optical output characteristics as the liquid crystal element to be driven and controlled is used, and the liquid crystal molecules of the liquid crystal element for a monitor are aligned. Since the state is detected and this detection signal is fed back in a feedback loop to create a drive signal, it becomes an inverse function to the optical output characteristics of the liquid crystal element that should be illuminated by the feedback amplifier in the feedback loop. Driving voltage can be created. Since this inverse function voltage is used to compensate or control the nonlinear characteristics of the liquid crystal element, it is possible to provide a liquid crystal element driving device with linear input/output characteristics with a relatively simple configuration. . In other words, the present invention allows easy construction of a highly reliable and low-cost autofocus lens, and also facilitates linear drive of variable focus liquid crystal lenses, liquid crystal dimming filters, and liquid crystal display elements, as well as control of characteristics relative to applied voltage. can be done.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an example of a liquid crystal element driving device according to the present invention, FIG. 2 is a graph showing transmission characteristics of a monitor liquid crystal element with respect to driving voltage, and FIG. 3 is a graph showing the transmission characteristics of a liquid crystal element to be driven and controlled. FIG. 4 is a graph showing focal length characteristics with respect to input voltage. FIG. 4 is a graph showing focal length characteristics with respect to driving voltage of a liquid crystal element for an automatic focusing lens. 1...Liquid crystal element 2...Liquid crystal element for monitor 3...Light source 4...Photodetector 5...
Feedback width modulator 6... Amplitude modulator 7... Oscillator

Claims (1)

[Claims] 1. A liquid crystal element for monitoring that has optical output characteristics almost the same as the optical output characteristics of the liquid crystal element whose drive is to be controlled;
A device for detecting the orientation state of liquid crystal molecules of the liquid crystal element for monitoring, and a device for detecting the orientation state of liquid crystal molecules of the liquid crystal element for monitoring, based on a detection signal from this detection device and an input signal indicating a desired optical output state of the liquid crystal element to be measured. A driving device for a liquid crystal element, comprising a feedback amplifier that generates an output signal for driving a liquid crystal element, and configured to drive a liquid crystal element to be driven and controlled based on the output signal from the feedback amplifier. .