Liquid crystal optical element, optical device, and aperture control method

An optical device comprising:

• a light source;
• a liquid crystal optical element which includes:
• a first substrate;
• a second substrate;
• a liquid crystal layer provided between said first and second substrates;
• an electrode pattern formed on one of said first and second substrates and having a first set of electrodes and a second set of electrodes disposed at an outer circumference of said first set of electrodes;
• a opposite electrode formed on the other one of said first and second substrates, said opposite electrode being opposed to said electrode pattern for applying a voltage therebetween,
• an objective lens for focusing light passed through said liquid crystal optical element;
• and
• a drive circuit configured to apply a plurality of voltage values to said first set of electrodes and said second set of electrodes such that a refractive index profile is formed within said liquid crystal layer, said refractive index profile causing incident light emitted from said light source and passing through said first set of electrodes to be directed to said objective lens for focusing at a focal point, and causing incident light passing through said second set of electrodes to diverge and to be prevented from being directed to said objective lens for focusing at said focal point, wherein:
• said second set of electrodes comprises at least three ring belt electrodes adjacent to each other;
• said drive circuit is configured to apply to a middle one of said three ring belt electrodes a first voltage value greater than second voltage values applied to the other two ring belt electrodes;
• and
• said drive circuit is configured to apply a third voltage value to one of said first set of electrodes immediately adjacent to said second set of electrodes so that said third voltage value is greater than said second voltage values.