Abstract: An improved electron deflection system for a light valve of the type used in Schlieren dark field projectors is disclosed. The deflection system eliminates one set (D box 25) of three sets of deflection electrodes used in such projectors. This is accomplished by modifying the d.c. voltages and a.c. voltages applied to the deflection electrodes. A quadrupole d.c. voltage is added to the first control box set of electrodes (61, 62) and a second quadrupole voltage of opposite sense is added to the focus deflection box set of electrodes (63, 65). This modifies the vertical and horizontal beam angles differentially and the vertical and horizontal beam trajectories differentially in a manner to compensate for the composite effects of spherical aberrations, deflection focusing aberrations, and the static starfish lens generated by the interaction of the square box electrode structure against the round drift ring assembly (21) of the deflection system.

Abstract: A laminar flow electron gun (16) for use in a light valve of the Schlieren dark field type is disclosed. The gun uses three accelerating electrodes (111, 112 and 113) with critical axial spacing to beam diameter ratios to allow independent adjustment and/or modulation of beam current density at the imaged aperture while reducing criticality of electrode voltages on the second and third accelerating electrodes. The design permits, but does not require, the use of a separate control grid electrode (110). The first accelerating electrode (111) is closely spaced to the cathode (119) to provide a virtual cathode at, or about, the voltage level of that electrode that reduces the thermal beam spread normally encountered in conventional electron guns. Primary control of the narrow angle beam current is by adjustment of the beam current density impinging on the final aperture (121) in the gun.

Abstract: A light valve of the Schlieren dark field type is provided with a vacuum envelope containing an electron gun, a focus and deflection assembly and a rotating disk coated with a light modulating fluid on which an electron beam from the electron gun is scanned in a raster pattern. The rotating disk has a transparent electrode which serves as as electron beam landing electrode. Between the focus and deflection assembly and the rotating disk is a drift ring assembly comprising at least two axially separated segments. The drift ring segment closest to the focus and deflection assembly is operated at a voltage to generate, in combination with the focus and deflection assembly, an electrostatic lens which corrects distortions that originate from deflection fields applied to the focus and deflection assembly.

Abstract: Elapsed time from turn-on of a fluid light valve to the time when the initial, turbulent fluid has settled to a quiescent condition on which a noise free image may be inscribed by an electron beam is reduced by expanding vertical sweep size of the raster, expanding horizontal sweep size of the raster, or reducing electron beam current. These operations, which may be controlled individually or in combination during the turn-on period, sweep out excess fluid from the raster area to ensure that fluid depth is adjusted to less than critical depth over the entire desired raster area so as to establish a smooth and uniform fluid surface by the time the turn-on sequence has been completed.