Abstract: An electron emission device comprises a P-type semiconductor layer which emits electron injected into the P-type semiconductor layer by utilizing the negative electron affinity state. At least one of said N-type semiconductor layer and the P-type semiconductor layer is made to have a super-lattice structure.

Abstract: An electron emitting apparatus comprising a plurality of electron emitting devices having an elongated electron emitting pattern which extends in a first direction. The adjacent electron emitting devices are arranged so as to be deviated in a second direction which crosses the first direction.

Abstract: A driving system is disclosed, wherein a potential gradient is formed in a pixel and is utilized for driving. Particularly, there is disclosed an optical modulation apparatus, comprising: a first substrate having thereon a conductor film, and a plurality of transmission lines disposed electrically connected to the conductor film; a second substrate; an optical modulation material disposed between the first and second substrate; and means for supplying a pair of electric signals in mutually opposite transmission directions to neighboring transmission lines among the plurality of transmission lines.

Abstract: A positioning device for positioning a mask having formed thereon a pattern to be transferred onto a semiconductor wafer. On the basis of a peripheral shape of the mask, the positioning device positions the mask so that a center of the mask is brought into alignment with a center of rotation of a holder for holding the mask. The positioning device includes a plurality of engaging pins to be engaged by the periphery of the mask, each engaging pin being movable in a direction toward the center of rotation of the mask holder. Movement of each of the engaging pins is controlled independently from the others, whereby the mask can be positioned irrespective of its size and/or shape.

Abstract: An electron emission device for attracting electrons emitted from an electron emission element to an anode, includes a current detector for detecting a flow-in current to said electron emission element and a flow-out current from the electron emission element. The difference between the flow-in current and the flow-out current is calculated and the voltage applied to the electron emission element is adjusted in accordance with the difference between the flow-in current and the flow-out cuttent.

Abstract: In a method of and an apparatus for controlling a fluid bearing, a state in which the power source of a control system is switched off (an open state) or a state in which a predetermined pressure different from the OFF condition is provided (a stopped state) is established when an abnormal condition in which the pressure reaches a predetermined value exceeding a servo-controlled upper or lower limit occurs, whereby the pressure of the fluid bearing is held within a safe pressure range.