Optical counting device

Claim 1

In combination with an electrical hand calculator, said calculator having a computer unit adapted to make mathematical calculations such as add, subtract, multiply and divide, said calculator including a digital display unit capable of displaying in digit form a numerical value determined by said computer unit, said calculator having a normally operable control panel employable to supply input into said computer unit to make said mathematical calculations, said control panel connected to an additive selection switch and a subtractive selection switch, upon actuation of said additive selection switch a predetermined numerical value is automatically added to the number displayed by said display unit with the then total accumulative value being displayed, upon actuation of said subtractive selection switch a predetermined numerical value is automatically subtracted to the number displayed by said display unit with the then total accumulative value being displayed, the improvement comprising: an optical counting apparatus located exteriorly of said electronic calculator and being electrically connected to both said additive and said subtractive selection switches, said counting apparatus capable of actuating said additive and said subtractive selection switches as though the actuation was performed by said control panel; a first interference device; a second interference device, said second interference device being movable with respect to said first interference device, both said first and said second interference devices having opaque areas and transparent areas, as said second interference device is moved said transparent areas are alignable permitting passage of light therethrough and also said opaque areas are alignable blocking the passage of light; a light producing means located adjacent said second interference device capable of projecting light through said transparent areas of said second interference device which subsequently is capable of being transmitted through said transparent area of said first interference device; light sensitive means located adjacent said first interference device, said light sensitive means being activated during the cycle of receiving no light to receiving light, upon activation of said light sensitive means an electrical signal is transmitted to a control means which thereupon causes activation of said electronic calculator; the size of the transparent areas on said first interference device being equal to the size of said opaque areas on said first interference device, the size of said transparent areas on said second interference device being equal in size to the size of said opaque areas on said second interference device, both said first interference device and said second interference device comprising a thin sheet of film; and the size of said transparent areas and said opaque areas on both said interference devices being equal in size.