Ink-jet recording apparatus

An ink jet recording apparatus comprising:

• at least one ink-droplet jetting nozzle having an orifice of defined aperture;
• a pressure chamber communicating with said at least one nozzle and having a flexible wall;
• an ink supply system for supplying ink from an ink reservoir to said pressure chamber of said at least one nozzle;
• said ink supply system comprising an ink chamber having a flexible diaphragm forming a wall thereof and which is deformable responsive to at least one of the ink pressure in said ink chamber and the amount of ink remaining in said ink chamber;
• said flexible diaphragm being deformable such that a displacement thereof responsive to an ink-pressure variation of -5 to -10 cm H.sub.2 O is from 5 .mu.m/cm H.sub.2 O to 20 mm/cm H.sub.2 O;
• a light shielding means coupled to said flexible diaphragm so as to be movable responsive to deformation of said flexible diaphragm;
• and
• light detecting means including a light emitting element and a light receiving element for receiving light emitted by said light emitting element, a light path being provided between said light emitting element and said light receiving element, said light detecting means being arranged adjacent said light shielding means;
• said light shielding means being selectively movable into and out of said light path to selectively block light emitted from said light emitting element from being received by said light receiving element as a function of the deformation of said flexible diaphragm.