Liquid-crystal light-amount adjusting device, method of driving liquid-crystal light-amount adjusting device, and camera including the liquid-crystal light-amount adjusting device

A method of driving a liquid-crystal light-amount adjusting device, comprising:

• acceleration driving pulses, having a frequency that is different from a frequency of driving pulses having a pulse shape in accordance with a desired optical transmittance, are supplied to the liquid crystal;
• dimming driving pulses, having a pulse shape in accordance with the desired optical transmittance, are supplied to the liquid crystal;
• changing an optical transmittance of the liquid-crystal in accordance with the pulse shapes of the acceleration driving pulses and dimming driving pulses supplied to the liquid crystal;
• detecting an ambient temperature of the liquid-crystal light-amount adjusting unit;
• and
• changing the respective frequencies of the acceleration driving pulses and the dimming driving pulses in accordance with the ambient temperature,
• wherein a frequency, a pulse amplitude, a duty ratio, and a first applying time of the acceleration driving pulses are based on the dimming driving pulses and a second applying time of the dimming driving pulses is determined from the first applying time,
• wherein the number of pulses in the acceleration driving pulses is an integer multiple of one period in the first applying time and the number of pulses in the dimming driving pulses is an integer multiple of one period in the second applying time.

A camera comprising:

• an optical system for focusing light coming from a target on an imaging surface;
• a liquid-crystal light-amount adjusting unit for adjusting an amount of the light that reaches the imaging surface, by changing an optical transmittance of a liquid crystal;
• a driving-pulse generating circuit for generating driving pulses having pulsed voltages, the driving pulses being supplied to the liquid crystal to change the optical transmittance;
• and
• a control circuit for controlling frequencies and duty ratios of the driving pulses;
• a temperature detecting circuit for detecting an ambient temperature of the liquid-crystal light-amount adjusting unit and outputting a result of detection to the control circuit, the control circuit changing the frequencies of the driving pulses in accordance with the ambient temperature,
• wherein the control circuit exercises control so that the driving-pulse generating circuit generates driving pulses for acceleration for a first applying time, having a first frequency and a first duty ratio, and driving pulses for dimming for a second applying time, having a second frequency that is different from the first frequency and a second duty ratio that is different from the first duty ratio,
• wherein the first frequency and the first duty ratio and the first applying time are based upon the driving pulses for dimming and the second applying time is determined from the first applying time,
• wherein the number of pulses in the driving pulses for acceleration is an integer multiple of one period in the first applying time and the number of pulses in the driving pulses for dimming is an integer multiple of one period in the second applying time.

A camera comprising:

• an optical system for focusing light coming from a target on an imaging surface;
• a liquid-crystal light-amount adjusting unit for adjusting an amount of the light that reaches the imaging surface, by changing an optical transmittance of a liquid crystal;
• a driving-pulse generating circuit for generating driving pulses having pulsed voltages, the driving pulses being supplied to the liquid crystal to change the optical transmittance;
• a control circuit for controlling a frequency and a duty ratio of the driving pulses;
• wherein the control circuit changes the frequency of the driving pulses during-imaging for one screen into a first applying time of driving pulses for acceleration and a second applying time for driving pulses for dimming;
• and
• a temperature detecting circuit for detecting an ambient temperature of the liquid-crystal light-amount adjusting unit and outputting a result of detection to the control circuit, the control circuit changing the frequencies of the driving pulses in accordance with the ambient temperature,
• wherein a first frequency and a first duty ratio and the first applying time of the driving pulses of accelerations are based upon the driving pulses for dimming and the second applying time is determined from the first applying time,
• wherein the number of pulses in the driving pulses for acceleration is an integer multiple of one period in the first applying time and the number of pulses in the driving pulses for dimming is an integer multiple of one period in the second applying time.