Control circuit for liquid crystal rear-vision mirror
First Claim
1. A control circuit of a rear-vision mirror including a liquid crystal mirror for use in automobiles, for automatically operating the liquid crystal mirror which reduces incident light during application of a driving voltage to the liquid crystal mirror, the circuit comprising:
- light sensing and comparing means for sensing incident light on a liquid crystal mirror, providing a sensor signal representing the amount of incident light, comparing the sensor signal with a predetermined reference signal to determine strength and weakness of the incident light, and providing a comparison signal indicating the amount of the incident light;
an Oscillator for receiving the comparison signal from said light sensing and comparing means and generating a square wave having a constant period;
pulse generating means for receiving the square wave from said oscillator and generating a pair of operating voltage driving pulses having amplitudes determined by a source voltage and having different phases; and
voltage driver means for buffering the driving pulses of said pulse generating means and providing the driving pulses to said liquid crystal rear-vision mirror.
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Accused Products
Abstract
A circuit for controlling a liquid crystal rear-vision mirror is disclosed. The liquid crystal rear-vision mirror is equipped in an automobile to sense the amount of lights incident upon the mirror itself from a headlight of another automobile following behind. When the level of incident lights goes higher than a pre-determined level, the circuit generates a pulse signal of a fixed period to make the liquid crystal shutter properly function so that the amount of said incident light reflecting from the mirror to the driver will be decreased to a level adequate to secure driving safety.
352 Citations
11 Claims
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1. A control circuit of a rear-vision mirror including a liquid crystal mirror for use in automobiles, for automatically operating the liquid crystal mirror which reduces incident light during application of a driving voltage to the liquid crystal mirror, the circuit comprising:
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light sensing and comparing means for sensing incident light on a liquid crystal mirror, providing a sensor signal representing the amount of incident light, comparing the sensor signal with a predetermined reference signal to determine strength and weakness of the incident light, and providing a comparison signal indicating the amount of the incident light; an Oscillator for receiving the comparison signal from said light sensing and comparing means and generating a square wave having a constant period; pulse generating means for receiving the square wave from said oscillator and generating a pair of operating voltage driving pulses having amplitudes determined by a source voltage and having different phases; and voltage driver means for buffering the driving pulses of said pulse generating means and providing the driving pulses to said liquid crystal rear-vision mirror. - View Dependent Claims (3, 4)
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2. A control circuit for a liquid crystal rear-vision mirror comprising:
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light sensing and comparing means for sensing light incident on a liquid crystal mirror, providing a sensor signal representing the amount of incident light, comparing the sensor signal with a reference signal to determine strength and weakness of the incident light, and providing a comparison signal indicating the amount of the incident light; DC-AC inverting means for receiving the comparison signal from said light sensing and comparing means, for oscillating by a predetermined period to convert a DC signal into an AC signal and output the AC signal in sinusoidal waveform to an upper transparent electrode of the liquid crystal rear-vision mirror; and a DC power supply for supplying a predetermined DC voltage signal to a lower transparent electrode of the liquid crystal rear-vision mirror whereby the liquid crystal rear-vision mirror is alternately operated by the signals applied to both the upper and lower transparent electrodes. - View Dependent Claims (5)
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6. A control circuit for a liquid crystal mirror, comprising:
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light sensing and comparing means for sensing light incident on a liquid crystal mirror, for providing a sensor signal representing the amount of incident light, for comparing the sensor signal with a predetermined reference signal to determine strength of the incident light, and for providing a comparison signal indicating the strength of the incident light; and means arranged to receive said comparison signal from said light sensing and comparing means, for generating and alternately applying to a first of two oppositely disposed electrodes of the liquid crystal mirror a first driving pulse exhibiting a constant period, an amplitude and a first phase, and to a second driving pulse exhibiting said constant period and a second phase different from said first phase. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification